WO2003054353A2 - Vertical cavity surface emitting laser including indium, antimony and nitrogen in the active region - Google Patents

Vertical cavity surface emitting laser including indium, antimony and nitrogen in the active region Download PDF

Info

Publication number
WO2003054353A2
WO2003054353A2 PCT/US2002/041736 US0241736W WO03054353A2 WO 2003054353 A2 WO2003054353 A2 WO 2003054353A2 US 0241736 W US0241736 W US 0241736W WO 03054353 A2 WO03054353 A2 WO 03054353A2
Authority
WO
WIPO (PCT)
Prior art keywords
vcsel
layers
barrier layers
quantum well
quantum wells
Prior art date
Application number
PCT/US2002/041736
Other languages
French (fr)
Other versions
WO2003054353A3 (en
Inventor
Ralph H. Johnson
Original Assignee
Honeywell International Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Honeywell International Inc. filed Critical Honeywell International Inc.
Publication of WO2003054353A2 publication Critical patent/WO2003054353A2/en
Publication of WO2003054353A3 publication Critical patent/WO2003054353A3/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
    • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
    • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/3211—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures characterised by special cladding layers, e.g. details on band-discontinuities
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/3235—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength longer than 1000 nm, e.g. InP-based 1300 nm and 1500 nm lasers
    • H01S5/32358—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength longer than 1000 nm, e.g. InP-based 1300 nm and 1500 nm lasers containing very small amounts, usually less than 1%, of an additional III or V compound to decrease the bandgap strongly in a non-linear way by the bowing effect
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/3235—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength longer than 1000 nm, e.g. InP-based 1300 nm and 1500 nm lasers
    • H01S5/32358—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength longer than 1000 nm, e.g. InP-based 1300 nm and 1500 nm lasers containing very small amounts, usually less than 1%, of an additional III or V compound to decrease the bandgap strongly in a non-linear way by the bowing effect
    • H01S5/32366—(In)GaAs with small amount of N
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/3403—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having a strained layer structure in which the strain performs a special function, e.g. general strain effects, strain versus polarisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34306—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength longer than 1000nm, e.g. InP based 1300 and 1500nm lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34346—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser characterised by the materials of the barrier layers
    • H01S5/34353—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser characterised by the materials of the barrier layers based on (AI)GaAs

Definitions

  • This invention relates to vertical cavity surface emitting lasers and more particularly to vertical cavity surface emitting lasers utilizing combinations of nitrogen, aluminum, antimony, phosphorous and/or indium as a material system and as a means to increase VCSEL device wavelength.
  • Solid-state semiconductor lasers are important devices in applications such as optoelectronic communication systems and high-speed printing systems. Recently, there has been an increased interest in vertical cavity surface emitting lasers (“VCSELs”) although edge emitting lasers are currently used in the vast majority of applications. A reason for the interest in VCSELs is that edge emitting lasers produce a beam with a large angular divergence, making efficient collection of the emitted beam more difficult. Furthermore, edge emitting lasers cannot be tested until the wafer is cleaved into individual devices, the edges of which form the mirror facets of each device. On the other hand, not only does the beam of a VCSEL have a small angular divergence, a
  • VCSEL emits light normal to the surface of the wafer.
  • VCSELs incorporate the mirrors monolithically in their design, they allow for on-wafer testing and the fabrication of one-dimensional or two-dimensional laser arrays.
  • VCSELs are typically made by growing several layers on a substrate material.
  • VCSELs include a first mirrored stack, formed on the substrate by semiconductor manufacturing techniques, an active region, formed on top of the first mirrored stack, and a second mirrored stack formed on top of the active region. By providing a first contact on top of the second mirrored stack, and a second contact on the backside of the substrate, a current is forced through the active region, thus driving the VCSEL.
  • the active region is made up further of one or more quantum wells sandwiched between two spacer cladding regions. Inside the spacers, the active region is sandwiched by confining layers. The confining layers or regions are used to provide electrical confinement of minority carriers.
  • a VCSEL generally may be grown or fabricated that generates light at a desirable, predetermined wavelength. For example, by using InGaAs quantum wells on GaAs substrates longer wavelength VCSELs can be produced. The use of InGaAs quantum wells, however, causes strain in the quantum wells. If the quantum wells are grown past their critical thickness, they relax by creating dislocations, and thus a poor quality active region.
  • the thickness of the various layers in the active region while not arbitrary have some flexibility within the constraints of the design and the process.
  • the combined thickness of the spacers, the confining layers, the barriers and the active regions sandwiched by the mirrors must be such that a Fabrey Perot resonator is formed.
  • the quantum wells should be positioned so that they are roughly centered at an antinode of the electric field. These two requirements define the spacer thickness in terms of the other layer thicknesses.
  • the barrier layer thicknesses between the quantum wells need to be thick enough to adequately define the quantum wells, but thin enough that the quantum well positions are not excessively far from the antinode of the electric field.
  • the thickness of the barrier layers at the boundaries of the quantum well regions have some flexibility.
  • the confining layers are often one in the same with the spacers or, as is shown in this work, can grade stepwise or continuously in the valence and conduction bands towards that of the barriers. Sometimes the confining layers and barrier layers are made from the same compositions, but this is not optimal for carrier confinement and is usually a compromise made for processing reasons.
  • the thickness of the quantum well is related by quantum mechanics to the well and barrier compositions, the desired emission wavelength, and the density of states. With a higher density of states narrower quantum wells can be optimally used.
  • What is needed in the VCSEL art are means to achieve long wavelength quantum wells normally fabricated on GaAs substrates.
  • the present inventor has recognized that it would be advantageous to remedy the foregoing and other deficiencies in the prior art, and to facilitate the easier production of longer wavelength VCSELs. Accordingly, the present invention is described and presented as a novel methods and means to address the shortcomings currently found in the art.
  • quantum wells and/or associated barrier layers can be grown with several novel combinations of nitrogen, aluminum, antimony, phosphorous and/or indium placed within or about a typical GaAs substrate to achieve long wavelength VCSEL performance, e.g., within the 1260 to 1650 nm range useful for fiberoptic communication.
  • a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) with confining regions comprised of AlGaAs.
  • a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) and the barrier layers.
  • a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) and barrier layers and aluminum is added to the confining layers.
  • a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) and Al is introduced in the barrier and confining layers.
  • a VCSEL is provided wherein InGaAs with Sb and >1 % N is added to the quantum well(s).
  • a VCSEL is provided wherein InGaAsN and Sb are introduced in the quantum well(s) and GaAsN is introduced in the barrier layers.
  • a VCSEL is provided wherein an InGaAsSbN quantum well is provided with GaAsP barrier layers and AlGaAs confinement layers.
  • a VCSEL is provided wherein InGaAs is provided in the quantum well(s) (no N) with GaAsN barrier layers and AlGaAs confining regions.
  • a VCSEL is provided wherein AlGaAs barrier layers are provided with at least one GaAs quantum well including N, Sb and/or In introduced in the quantum well(s).
  • Nitrogen can be added to the barrier layers of the InGaAs quantum wells of a VCSEL such that the barrier layers are in tension while the quantum wells are in compression.
  • quantum well thickness can be reduced. Nitrogen can be useful for strain compensation and overall band gap reduction within the active region.
  • AIGaAsN can be used for minority carrier confinement in the barrier layers to avoid type 2 behavior in the valence band.
  • Nitrogen or nitrogen and Sb can be used in GaAs or InGaAs quantum wells.
  • the Sb and nitrogen are balanced to avoid a type 2 transition in either the valence band or the conduction band and maintain excellent carrier confinement with at least a 0.1 ev band discontinuity of both the valence and conduction bands at the quantum well edge.
  • a vertical cavity surface emitting laser can include at least one quantum well comprised of InGaAsSbN; barrier layers sandwiching said at least one quantum well; and confinement layers sandwiching said barrier layers. Confinement and barrier layers can comprise AlGaAs. Barrier layer, in the alternative, can also comprise GaAsP. Nitrogen can be placed in the quantum wells.
  • Quantum wells can be developed up to and including 50 A in thickness. Quantum wells can also be developed with a depth of at least 40 meV. BRIEF DESCRIPTION OF THE DRAWINGS
  • Figure 1 is a graphical illustration of energy v. position and strain for a VCSEL having AlGaAs confinement areas, GaAs barrier layers and InGaAs quantum wells;
  • Figure 2 is a graphical illustration of "energy v. position" and “strain” for a VCSEL having AlGaAs confinement layers, GaAs barrier layers and InGaAsN quantum wells;
  • Figure 3 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAsN barrier layers and InGaAsN quantum wells;
  • Figure 4 is a graphical illustration of "energy v. position" and "strain" for a
  • VCSEL having AlGaAs confinement layers, GaAsN barrier layers and InGaAsN quantum wells;
  • Figure 5 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAsN barrier layers and InGaAsNSb quantum wells;
  • Figure 6 is a graphical illustration of "energy v. position” and “strain” for a VCSEL having GaAs barrier layers and GalnAsNSb quantum wells
  • Figure 7 is a graphical illustration of "energy v. position” and “strain” for a VCSEL having AlGaAs barrier layers and InGaAsN quantum wells;
  • Figure 8 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAs barrier layers and GaAsNSb quantum wells with >1 % nitrogen;
  • Figure 9 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having AlGaAs confinement layers, GaAsN barrier layers and InGaAs quantum wells;
  • Figure 10 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAsN barrier layers and GaAsNSb quantum wells;
  • Figure 11 is a graphical illustration of "energy v. position" and “strain” for a VCSEL having AlGaAs confinement layers, GaAsP barrier layers and GaAsSbN quantum wells;
  • Figure 12 is an exemplary sectional view of a VCSEL in accordance with an embodiment of the present invention.
  • Figure 13 is another exemplary sectional view of a VCSEL in accordance with another embodiment of the present invention.
  • Figure 14 is a graphical illustration of "energy v. position" for a VCSEL having three quantum wells with depths of -125 meV for valence bands and -250 meV for conduction bands;
  • Figure 15 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 14 wherein recombination within the quantum wells is shown;
  • Figure 16 is a graphical illustration of "energy v. position” for the VCSEL of FIG. 14 wherein total power within the quantum wells is shown;
  • Figure 17 is a graphical illustration of "energy v. position" for a VCSEL having three quantum wells with depths of -60 meV for valence bands and -120 meV for conduction bands;
  • Figure 18 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 17 wherein recombination within the quantum wells is shown;
  • Figure 19 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 17 wherein total power within the quantum wells is shown;
  • Figure 20 is a graphical illustration of "energy v. position" for a VCSEL having three quantum wells with depths of -40 meV for valence bands and -80 meV for conduction bands;
  • Figure 21 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 21 wherein recombination within the quantum wells is shown;
  • Figure 22 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 21 wherein total power within the quantum wells is shown.
  • This invention can use strain compensation with or without nitrogen in the barrier layers to allow more indium and/or Sb incorporation in the quantum wells without relaxation and thus achieve longer wavelengths.
  • a trade off of the effects on well depth of the Sb and N can also be accomplished so that conduction band wells of at least 0.07 ev and valence band wells of at least 0.05 ev are achievable.
  • Figures 1 -1 1 will now be provided prior to describing the benefits of the invention in detail. Referring to Figure 1 , portions of the illustrations in Figure 1 -11 on the left hand-side of the drawings are meant to graphically represent the position of a quantum well 11 , barrier layers 12, and confinement layers 13 of a VCSEL. Power is represented by drawing lines made vertically with respect to the position of the components mentioned. On the right hand of Figures 1 -1 1 , strain for each illustrated device is also shown graphically, with compression also being represented vertically downwards and tension represented vertically upwards.
  • FIG. 1 a graphical illustration of "energy v. position" and “strain” for a VCSEL having AlGaAs confinement layers 13, GaAs barrier layers 12 and an InGaAs quantum well 1 1 is shown and will serve as a benchmark for adjustments made in Figures 2-1 1.
  • a InGaAs quantum well on a GaAs substrate longer wavelengths can be achieved, however, strain is also caused in the quantum well as shown by the depth 15 of the associated strain measurement.
  • a VCSEL having AlGaAs confinement layers, GaAs barrier layers and a InGaAsN quantum well.
  • Nitrogen is added to the InGaAs quantum well of Figure 1 , which resulted in a decrease 20 in energy and valence band confinement.
  • strain was reduced 22 when compared to the nitrogen-free device of Figure 1 .
  • nitrogen (N) is also added to the barrier layers of the device shown in Figure 2. As shown by the arrows 31 in Figure 3, the hole well is recreated with the introduction of nitrogen in the barrier layers.
  • strain compensation 33 was provided to the device with the addition of nitrogen to the barrier layers.
  • antimony (Sb) is now added to the quantum well of the device previously viewed in Figure 4.
  • the introduction of Sb to the quantum well causes a decrease in the band gap, an increase in the valence band well, and a decrease in the conduction band well. Strain in the device is increased with the introduction of Sb.
  • antimony (Sb) was added to the quantum well for the device illustrated in Figure 2.
  • the band gap for the device increases the valence band well 61 , but decreases the conduction band well 62.
  • Compressive strain in the quantum well is also shown to increase with Sb.
  • a Indium free device is shown. Indium is removed from the device shown graphed in Figure 6.
  • the quantum well includes GaAsNSb. Device strain is shown to improve with the removal of In.
  • N is shown to be removed from the quantum well for the device shown in Figure 4.
  • the removal of N from the quantum well increases band gap and hole confinement. Strain, however, is also increased in the quantum well, but is compensated for in the barrier region.
  • a strain compensated device is illustrated.
  • the device of Figure 8 is improved by adding nitrogen to the barrier layers and aluminum to the confining layers.
  • the quantum well is GaAsSbN. This combination increases the hole well and decreases the electron well. The overall strain in the device is reduced.
  • FIG. 11 additional strain compensation is shown by adding phosphorous (P) to the barrier layers.
  • the device in Figure 11 is shown to have AlGaAs confinement layers, and a GaAsSbN quantum well. Indium can also be used in the quantum well.
  • Figure 8 shows a GaAsSbN quantum well with GaAs barriers.
  • both Sb and nitrogen lower the band gap.
  • the Sb causes the quantum well to tend towards poor electron confinement with good hole confinement, and the nitrogen tends to go in the opposite direction towards poor hole confinement and good electron confinement.
  • invention aspect 1 can be combined with this to compensate the excessive compressive strain. That is nitrogen or phosphorous can be added to the barriers layers because it tends to deepen the electron well which the Sb in the quantum well tends to shallow the electron well. It is also useful to increase the gap of the confining layers with Al or even P once again to avoid extra wells.
  • Indium can be used in the quantum well of invention to adjust the wavelength, well depths and strain in the quantum wells. As the band gap shrinks, the wells become more compressive. But adding indium has only a secondary effect on the relative band offsets (valence band or conduction band) as shown in Figures 5 and 6. Fig 6 will work for both 1310 nm and 1550 nm active regions.
  • AlGaAs barrier layers can be used for InGaAsN quantum wells to increase the hole well depth. Because nitrogen increases the electron effective mass the quantum wells containing nitrogen can be made thinner, that is less than 50 A. In VCSELs, this means there are more quantum wells.
  • All aspects of the present invention can apply to single as well as multiple quantum wells in both edge emitters and VCSELs and other semiconductor lasers.
  • at least a 0.07 ev well depth is maintained in the conduction band, and a 0.05 ev depth is maintained in the valence band.
  • Epi flattening techniques which reduce the bunching of steps, can be used in combination with the above.
  • Intra-quantum well mechanical stabilizers can also be used with the above.
  • VCSEL vertical cavity surface emitting laser 100
  • the VCSEL 100 can be grown by techniques such as metal organic molecular beam epitaxy, or metal-organic chemical vapor deposition. Reference is made to U.S. Patent No. 5,903,589, assigned to the assignee for the present invention, which describes methods of VCSEL fabrication use in the art.
  • the VCSEL can preferably be grown on a GaAs substrate 101 due to the robust nature and low cost of the material, however it should be recognized that semiconductor materials, Ge for example, could also be used as the substrate.
  • the VCSEL 100 can then be formed by disposing layers on the substrate.
  • Epitaxial layers can include: a first mirror stack 105 disposed on the substrate 101 , a first cladding region 108 disposed on the first mirror stack 105, an active region 110 disposed on the first cladding region 108, a second cladding region 112 disposed on the active region 110, and a second mirror stack 115 disposed on the second cladding region 112.
  • the active region 110 can further includes one or more quantum wells 120 being separated from each other by barrier layers 125, depending on the application for which the VCSEL 100 is designed.
  • barrier layers 125 depending on the application for which the VCSEL 100 is designed.
  • One of ordinary skill in the art can find it obvious to differ the number of quantum wells 120 in the VCSEL active region 110.
  • the first mirror stack 105 can be grown by epitaxially depositing mirror pair layers 106 on the substrate 101.
  • a suitable semiconductor material system for the mirrored pairs 106 should be deposited.
  • the substrate 101 is GaAs, therefore a GaAs/AIGaAs material system can be employed.
  • the number of mirror pair layers 106 in the stack 105 can usually range from 20 to 40, depending on the difference between the refractive indices of the layers. Different refractive indexes are also achievable by altering the Aluminum content in the mirror stack 105.
  • a first cladding region 108 can be made of one or more layers epitaxially disposed on the first mirror stack 105.
  • the first cladding region 108 in the currently described embodiment of the invention can be made of a GaAsN material system.
  • Nitrogen added to the quantum well 120 can have the effect of increasing the strain between the layers, which reduces the band gap energy of the excited state. Band gap energy reduction generally decreases the amount of energy required to excite the material, and increases the wavelength of the emitted photon. This can be desirable to achieve longer wavelength VCSELs 100. The more Nitrogen that is added to the quantum well 120, the greater this reduction in band gap energy can be, and thus longer wavelength VCSELs 100 can be produced.
  • the strain in the structure can be reduced, which can increase the allowable thickness of the quantum wells, and the energy gap can be reduced both which can increases the allowable wavelength.
  • the use of nitrogen in the quantum wells can make the valence band discontinuity nonconfining or type 2.
  • AlGaAs or AIGaAsN as the confining material, however, and GaAsN, AlGaAs, or AIGaAsN or GaAsP barrier layers, the nonconfining problem can also be reduced.
  • Sb replaces a portion of the As in the quantum well, the type II transition caused by nitrogen can further be avoided allowing even more nitrogen. Because even more nitrogen is allowable, more indium is also allowable. Because nitrogen, indium, and Sb all reduce the band gap energy, the achievable wavelengths extend to wavelengths longer than either 1310nm used for datacom or 1550 nm used for telecom.
  • the overall strain in the well can become significantly less allowing more indium before reaching the critical thickness, thus making longer wavelength VCSELs possible.
  • the allowable strain in the quantum well region can increase meaning even more indium can be used in the quantum wells. More indium is allowable without violating the critical thickness, making for an even lower band gap and longer wavelengths.
  • using nitrogen in the barrier layers between the quantum wells can also reduce the energy of these barriers in the conduction band making the energy of the quantum state lower, further increasing the allowable wavelength.
  • Using nitrogen in the barrier layers can also be advantageous in avoiding type II behavior in the valence band because as nitrogen is incorporated in the quantum wells, the conduction band discontinuity increases, and the valence band discontinuity decreases.
  • use of AlGaAs or AIGaAsN for the confining structure can further avoid unintentional wells in the valence band at the barrier layer confining layer boundary.
  • the use of Sb in the quantum well can reduce the band gap energy further, while avoiding the type II behavior (allowing even more nitrogen). All of these aspects contribute to the ability to create very long wavelength active regions.
  • Introducing Nitrogen into the active region 110 is not generally without drawbacks. GaN and InN can have large differences in their lattice constants as well as optimal growth conditions.
  • the quality of the material can be greatly compromised when layers comprising the active region 110 are grown beyond a certain critical thickness. Layers thicker than this critical thickness can have misfit dislocations, relaxing the strain between the layers, and decreasing the material quality. This can substantially compromises the quality of the VCSEL 100.
  • the band gap energy decrease can be observed as it is when Nitrogen is added only to the active region 110.
  • the amount of Nitrogen that is needed in the active region 110 to achieve a given band gap energy reduction, and therefore a longer wavelength can be reduced.
  • the lattice mismatch can therefore not generally be as severe as when Nitrogen is added to the active region 110 alone, thus making the material system easier to fabricate.
  • Higher quality VCSELs can be achieved by introducing Nitrogen into the barrier regions125 than when Nitrogen is only added to the active region 110.
  • Active region 110 can next be epitaxially deposited on the first cladding region 108.
  • the active region 110 can include one or more quantum wells 120.
  • the preferred embodiment uses quantum wells 120 of less than 50 angstroms.
  • Nitrogen is introduced into the active region 110 or the cladding region 108, 112
  • the effective electron mass in the regions can increase dramatically. With this increased density of the states, the amount of Indium or Nitrogen needed to produce a given amount of gain in the active region 110 generally decreases. Therefore, the volume of the quantum well 120 can also be decreased, giving less volume for parasitics to occur in.
  • a second cladding region 112 can be made of one or more layers epitaxially disposed on the active region 110.
  • the second cladding region 112 can be made of a GaAsN material system.
  • a second mirror stack 115 can next be grown by epitaxially depositing mirror pairs layers 116 on the second cladding region 115.
  • a suitable semiconductor material system for the mirrored pairs 116 should be deposited.
  • the substrate 101 is formed of GaAs, therefore a GaAs/AIGaAs material system can be employed.
  • the number of mirror pair layers 116 in the stack 115 can usually range from 20 to 40, depending on the difference between the refractive indices of the layers. Different refractive indexes are achievable by altering the Aluminum content in the mirror stack 115.
  • a flattening layer 235 can be sandwiched between the lower confining layer and the quantum wells.
  • bunching of molecular steps form on the surface of the newly formed layers.
  • the steps on the layer's surface increase the likelihood that layers adjacent to the substrate can dislocate from the substrate.
  • a heavily compressively strained InGaAs flattening layer 235 grown before the active region 210 at a distance sufficient to minimize the straining effects on the quantum well layers generally has the effect of flattening the surface to which the active region 210 is disposed.
  • the distance between the flattening layer 235 and the quantum wells can be several hundred angstroms.
  • This flattening layer 235 between the lower confining layer 201 and the first mirror stack 205 flattens out these molecular steps.
  • the surface can be further flattened when the epi layers are grown on "100 or 111 on" orientation substrates. If the substrate is in "off" orientation, the number of molecular steps can increase and the likelihood of bunching of steps increases, thereby increasing the likelihood for dislocation.
  • the strain between layers can be further increased through the addition of greater amounts of In or Sb in the active region. This increased In or Sb generally decreases the band gap energy, thereby making it easier to grow VCSELs 201 that emit longer wavelengths.
  • Quantum well depth can be an important consideration in achieving optimal gain from VCSEL quantum wells.
  • Comprehensive, up-to-date compilations of band parameters useful for the development of semiconductor devices, such as VCSELS, are generally discussed in a paper entitled "Band parameters for lll-V compound semiconductors and their alloys," by Vurgraftman, Meyer and Ram-Mohan (Journal of Applied Physics, Volume 89, Number 1 1 , 1 June 2001 ). The paper provides some insight for the skilled in the art on calculating band offsets, thereby enabling the achievement of optimal quantum well depth utilizing various materials, and is hereby incorporated by reference into the present disclosure for its teaching.
  • Quantum wells for VCSELs should be designed in order to promote confinement of carriers within the quantum wells instead of outside of the quantum wells, while at the same time not being so deep as to prohibit adequate flow of carriers between the wells. Proper quantum well depth will maximize the gain in the quantum wells of a VCSEL, which minimizes the threshold current and maximizes slope efficiency (both desirable outcomes). Luminescence and gain within a quantum well is related to the product of holes and electrons within the quantum well. Quantum well depth is established by setting band offsets. Two bands used to determine the quantum well depth are the valence and conduction bands (the valence band associated with hole wells and the conduction band with electron wells). Setting of the bands determines the offsets (meV, mili electron volts) for the quantum well and provides depth associated with the confinement of holes and electrons.
  • Figures 14-22 provide graphical illustrations of VCSEL behavior at different well depths. Although the simulations illustrated in Figures 14-22 were conducted on AlGaAs quantum wells, the overall analysis is applicable to other materials since temperature will generally be the same and effective masses are not vastly different between devices.
  • Figures 14-16 are a first group of graphs representing the analysis of a normal set of three quantum wells 1401 for an 850 nm VCSEL under bias (actively lasing). In this case there is substantial p-doping, which suppresses the electron concentration relative to the hole concentration.
  • well depth of three quantum wells 1401 was established by setting the valence band offsets 1405 at approximately 125 meV and the conduction band offset 1410 at 250 meV. It should be appreciated that the quantum well number does not have to be limited to three. As can be seen within the graphical data in FIG. 15, there is little recombination outside the three quantum wells shown.
  • FIG. 17-19 illustrate a second group of graphs representing the analysis of quantum wells under bias.
  • quantum well depths were set at approximately 60 meV for valence bands 1703 and 120 meV for conduction bands 1705.
  • FIG. 18 there is shown an increasing number of holes and electrons 181 1 outside the three quantum wells. Such loss of holes and electrons outside of the quantum wells results in less luminescence 1901 and, therefore, less gain resulting from the quantum wells as shown in FIG. 19
  • Figures 20-22 are a third group of graphs representing the analysis of quantum wells under bias.
  • the well depths for the three quantum wells were set at approximately 40 meV for valence bands 2003 and 80 meV for conduction bands 2005.
  • recombination 2101 outside of the three quantum wells has become quite large.
  • loss of recombination within the quantum wells results in a significantly less luminescence 2201 and gain due to undesirable parasitic luminescence 2205.
  • VCSELs having quantum wells hole depths of at least 40 MeV and electron depths of at least 80 MeV.
  • Such a setting for the valence and conduction bands would provide at least minimally acceptable gain; however, optimal quantum well hole well depths have been shown to be up to and including 125 MeV for the Valence bands and conduction bands with a setting of up to and including 250 MeV.
  • Well depths even greater may be acceptable, as long as sufficient transport between the wells is maintained by thermionic emission, tunneling, or both.

Abstract

Quantum wells and associated barrier layers can be grown to include nitrogen (N), aluminum (AI), antimony (Sb), phosphorous (P) and/or indium (In) placed within or about a typical GaAs substrate to achieve long wavelength VCSEL performance, e.g., within the 1260 to 1650 nm range. In accordance with features of the present invention, a vertical cavity surface emitting laser (VCSEL) can include at least one quantum well (11) comprised of InGaAsSbN; barrier layers (12) sandwiching said at least one quantum well (11); and confinement layers (13) sandwiching said barrier layers (12). Confinement (13) and barrier layers 12 can comprise AlGaAs. Barrier layer, in the alternative, can also comprise GaAsP. Nitrogen can be placed in the quantum wells (11). Quantum wells can be developed up to and including 50 Å in thickness. Quantum wells can also be developed with a depth of at least 40 meV.

Description

VERTICAL CAVITY SURFACE EMITTING LASER INCLUDING INDIUM, ANTIMONY AND NITROGEN IN THE ACTIVE REGION
TECHNICAL FIELD This invention relates to vertical cavity surface emitting lasers and more particularly to vertical cavity surface emitting lasers utilizing combinations of nitrogen, aluminum, antimony, phosphorous and/or indium as a material system and as a means to increase VCSEL device wavelength.
BACKGROUND OF THE INVENTION
Solid-state semiconductor lasers are important devices in applications such as optoelectronic communication systems and high-speed printing systems. Recently, there has been an increased interest in vertical cavity surface emitting lasers ("VCSELs") although edge emitting lasers are currently used in the vast majority of applications. A reason for the interest in VCSELs is that edge emitting lasers produce a beam with a large angular divergence, making efficient collection of the emitted beam more difficult. Furthermore, edge emitting lasers cannot be tested until the wafer is cleaved into individual devices, the edges of which form the mirror facets of each device. On the other hand, not only does the beam of a VCSEL have a small angular divergence, a
VCSEL emits light normal to the surface of the wafer. In addition, since VCSELs incorporate the mirrors monolithically in their design, they allow for on-wafer testing and the fabrication of one-dimensional or two-dimensional laser arrays.
VCSELs are typically made by growing several layers on a substrate material. VCSELs include a first mirrored stack, formed on the substrate by semiconductor manufacturing techniques, an active region, formed on top of the first mirrored stack, and a second mirrored stack formed on top of the active region. By providing a first contact on top of the second mirrored stack, and a second contact on the backside of the substrate, a current is forced through the active region, thus driving the VCSEL.
The active region is made up further of one or more quantum wells sandwiched between two spacer cladding regions. Inside the spacers, the active region is sandwiched by confining layers. The confining layers or regions are used to provide electrical confinement of minority carriers. By selecting the appropriate materials for the quantum well, the confining layers, and the barrier layers, a VCSEL generally may be grown or fabricated that generates light at a desirable, predetermined wavelength. For example, by using InGaAs quantum wells on GaAs substrates longer wavelength VCSELs can be produced. The use of InGaAs quantum wells, however, causes strain in the quantum wells. If the quantum wells are grown past their critical thickness, they relax by creating dislocations, and thus a poor quality active region.
The thickness of the various layers in the active region while not arbitrary have some flexibility within the constraints of the design and the process. The combined thickness of the spacers, the confining layers, the barriers and the active regions sandwiched by the mirrors must be such that a Fabrey Perot resonator is formed. The quantum wells should be positioned so that they are roughly centered at an antinode of the electric field. These two requirements define the spacer thickness in terms of the other layer thicknesses. The barrier layer thicknesses between the quantum wells need to be thick enough to adequately define the quantum wells, but thin enough that the quantum well positions are not excessively far from the antinode of the electric field. The thickness of the barrier layers at the boundaries of the quantum well regions have some flexibility. Optimally they need to be at least thick enough that the energy levels of each of the quantum wells is nominally the same. They can be thicker if material quality issues require this. The confining layers are often one in the same with the spacers or, as is shown in this work, can grade stepwise or continuously in the valence and conduction bands towards that of the barriers. Sometimes the confining layers and barrier layers are made from the same compositions, but this is not optimal for carrier confinement and is usually a compromise made for processing reasons.
The thickness of the quantum well is related by quantum mechanics to the well and barrier compositions, the desired emission wavelength, and the density of states. With a higher density of states narrower quantum wells can be optimally used. What is needed in the VCSEL art are means to achieve long wavelength quantum wells normally fabricated on GaAs substrates. The present inventor has recognized that it would be advantageous to remedy the foregoing and other deficiencies in the prior art, and to facilitate the easier production of longer wavelength VCSELs. Accordingly, the present invention is described and presented as a novel methods and means to address the shortcomings currently found in the art.
SUMMARY OF THE INVENTION The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention, and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. Additional objects and advantages of the current invention will become apparent to one of ordinary skill in the art upon reading the specification.
In accordance with addressing the limitations of the prior art, presented are new and improved features applied to the solid state laser art that are capable of providing longer wavelength VCSEL devices.
It is a feature of the present invention to provide a method of fabricating improved VCSELs.
In accordance with various aspects of the present invention, quantum wells and/or associated barrier layers can be grown with several novel combinations of nitrogen, aluminum, antimony, phosphorous and/or indium placed within or about a typical GaAs substrate to achieve long wavelength VCSEL performance, e.g., within the 1260 to 1650 nm range useful for fiberoptic communication.
In accordance with a feature of the present invention, a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) with confining regions comprised of AlGaAs. In accordance with another feature of the present invention, a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) and the barrier layers.
In accordance with another feature of the present invention, a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) and barrier layers and aluminum is added to the confining layers.
In accordance with another feature of the present invention, a VCSEL is provided wherein InGaAs with N is introduced in the quantum well(s) and Al is introduced in the barrier and confining layers.
In accordance with another feature of the present invention, a VCSEL is provided wherein InGaAs with Sb and >1 % N is added to the quantum well(s).
In accordance with another feature of the present invention, a VCSEL is provided wherein InGaAsN and Sb are introduced in the quantum well(s) and GaAsN is introduced in the barrier layers.
In accordance with another feature of the present invention, a VCSEL is provided wherein an InGaAsSbN quantum well is provided with GaAsP barrier layers and AlGaAs confinement layers.
In accordance with another feature of the present invention, a VCSEL is provided wherein InGaAs is provided in the quantum well(s) (no N) with GaAsN barrier layers and AlGaAs confining regions.
In accordance with another feature of the present invention, a VCSEL is provided wherein AlGaAs barrier layers are provided with at least one GaAs quantum well including N, Sb and/or In introduced in the quantum well(s). In accordance with another aspect of the present invention, Nitrogen can be added to the barrier layers of the InGaAs quantum wells of a VCSEL such that the barrier layers are in tension while the quantum wells are in compression. To compensate for the property changes inherent with the addition of Nitrogen to InGaAs quantum wells, quantum well thickness can be reduced. Nitrogen can be useful for strain compensation and overall band gap reduction within the active region.
In accordance with another feature of the present invention, AlGaAs or
AIGaAsN can be used for minority carrier confinement in the barrier layers to avoid type 2 behavior in the valence band.
In accordance with another feature of the present invention, Nitrogen or nitrogen and Sb can be used in GaAs or InGaAs quantum wells. The Sb and nitrogen are balanced to avoid a type 2 transition in either the valence band or the conduction band and maintain excellent carrier confinement with at least a 0.1 ev band discontinuity of both the valence and conduction bands at the quantum well edge.
In accordance with features of the present invention, a vertical cavity surface emitting laser (VCSEL) can include at least one quantum well comprised of InGaAsSbN; barrier layers sandwiching said at least one quantum well; and confinement layers sandwiching said barrier layers. Confinement and barrier layers can comprise AlGaAs. Barrier layer, in the alternative, can also comprise GaAsP. Nitrogen can be placed in the quantum wells.
Quantum wells can be developed up to and including 50 A in thickness. Quantum wells can also be developed with a depth of at least 40 meV. BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and from part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.
Figure 1 is a graphical illustration of energy v. position and strain for a VCSEL having AlGaAs confinement areas, GaAs barrier layers and InGaAs quantum wells;
Figure 2 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having AlGaAs confinement layers, GaAs barrier layers and InGaAsN quantum wells;
Figure 3 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAsN barrier layers and InGaAsN quantum wells;
Figure 4 is a graphical illustration of "energy v. position" and "strain" for a
VCSEL having AlGaAs confinement layers, GaAsN barrier layers and InGaAsN quantum wells;
Figure 5 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAsN barrier layers and InGaAsNSb quantum wells;
Figure 6 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAs barrier layers and GalnAsNSb quantum wells; Figure 7 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having AlGaAs barrier layers and InGaAsN quantum wells;
Figure 8 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAs barrier layers and GaAsNSb quantum wells with >1 % nitrogen;
Figure 9 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having AlGaAs confinement layers, GaAsN barrier layers and InGaAs quantum wells;
Figure 10 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having GaAsN barrier layers and GaAsNSb quantum wells;
Figure 11 is a graphical illustration of "energy v. position" and "strain" for a VCSEL having AlGaAs confinement layers, GaAsP barrier layers and GaAsSbN quantum wells;
Figure 12 is an exemplary sectional view of a VCSEL in accordance with an embodiment of the present invention;
Figure 13 is another exemplary sectional view of a VCSEL in accordance with another embodiment of the present invention;
Figure 14 is a graphical illustration of "energy v. position" for a VCSEL having three quantum wells with depths of -125 meV for valence bands and -250 meV for conduction bands;
Figure 15 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 14 wherein recombination within the quantum wells is shown; Figure 16 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 14 wherein total power within the quantum wells is shown;
Figure 17 is a graphical illustration of "energy v. position" for a VCSEL having three quantum wells with depths of -60 meV for valence bands and -120 meV for conduction bands;
Figure 18 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 17 wherein recombination within the quantum wells is shown;
Figure 19 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 17 wherein total power within the quantum wells is shown;
Figure 20 is a graphical illustration of "energy v. position" for a VCSEL having three quantum wells with depths of -40 meV for valence bands and -80 meV for conduction bands;
Figure 21 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 21 wherein recombination within the quantum wells is shown; and
Figure 22 is a graphical illustration of "energy v. position" for the VCSEL of FIG. 21 wherein total power within the quantum wells is shown.
DETAILED DESCRIPTION OF THE INVENTION
The novel features of the present invention will become apparent to those of skill in the art upon examination of the following detailed description of the invention or can be learned by practice of the present invention. It should be understood, however, that the detailed description of the invention and the specific examples presented, while indicating certain embodiments of the present invention, are provided for illustration purposes only because various changes and modifications within the scope of the invention will become apparent to those of skill in the art from the detailed description of the invention and claims that follow.
Making long wavelength quantum wells on GaAs has proven to be very difficult, but technology presented in this the following description has advanced to the point that longer wavelength quantum wells and higher efficiency VCSELs are now feasible. One issue is that long wavelength compounds tend to not be lattice matched to GaAs. This has been alleviated recently using nitrogen in the quantum wells, which reduces the energy band and reduces the lattice constant in contrast to every other band gap reducing element, thus allowing the inclusion of other elements (e.g., In, Sb), and which reduces the band gap but increases the lattice constant. Unfortunately, the use of nitrogen can have the negative aspect of reducing confinement in the valence band and may tend to make poorer utility material as more nitrogen is added.
This invention can use strain compensation with or without nitrogen in the barrier layers to allow more indium and/or Sb incorporation in the quantum wells without relaxation and thus achieve longer wavelengths. A trade off of the effects on well depth of the Sb and N can also be accomplished so that conduction band wells of at least 0.07 ev and valence band wells of at least 0.05 ev are achievable. A preliminary description to Figures 1 -1 1 will now be provided prior to describing the benefits of the invention in detail. Referring to Figure 1 , portions of the illustrations in Figure 1 -11 on the left hand-side of the drawings are meant to graphically represent the position of a quantum well 11 , barrier layers 12, and confinement layers 13 of a VCSEL. Power is represented by drawing lines made vertically with respect to the position of the components mentioned. On the right hand of Figures 1 -1 1 , strain for each illustrated device is also shown graphically, with compression also being represented vertically downwards and tension represented vertically upwards.
Referring to Figure 1 , a graphical illustration of "energy v. position" and "strain" for a VCSEL having AlGaAs confinement layers 13, GaAs barrier layers 12 and an InGaAs quantum well 1 1 is shown and will serve as a benchmark for adjustments made in Figures 2-1 1. With use of a InGaAs quantum well on a GaAs substrate, longer wavelengths can be achieved, however, strain is also caused in the quantum well as shown by the depth 15 of the associated strain measurement.
Referring to Figure 2, a VCSEL is shown having AlGaAs confinement layers, GaAs barrier layers and a InGaAsN quantum well. Nitrogen is added to the InGaAs quantum well of Figure 1 , which resulted in a decrease 20 in energy and valence band confinement. Here in Figure.2, however, strain was reduced 22 when compared to the nitrogen-free device of Figure 1 . Referring to Figure 3, nitrogen (N) is also added to the barrier layers of the device shown in Figure 2. As shown by the arrows 31 in Figure 3, the hole well is recreated with the introduction of nitrogen in the barrier layers. In addition, strain compensation 33 was provided to the device with the addition of nitrogen to the barrier layers. It should be noted that strain compensation would be realized even where nitrogen is not also introduced in the quantum well. Referring to Figure 4, aluminum (Al) is now added to the confinement layers/areas of the device shown in Figure 3. Providing Al to the confinement layers eliminates or substantially reduces undesirable wells at the edges of the device as shown by the arrows 41 in the figure. The introduction of aluminum, however, has a negligible effect on the devices strain.
Referring to Figure 5, antimony (Sb) is now added to the quantum well of the device previously viewed in Figure 4. The introduction of Sb to the quantum well causes a decrease in the band gap, an increase in the valence band well, and a decrease in the conduction band well. Strain in the device is increased with the introduction of Sb.
Referring to Figure 6, antimony (Sb) was added to the quantum well for the device illustrated in Figure 2. The band gap for the device increases the valence band well 61 , but decreases the conduction band well 62. Compressive strain in the quantum well is also shown to increase with Sb.
Referring to Figure 7, aluminum (Al) is added to the barrier and confining layers of the device first shown in Figure 2. As seen in the graphical illustration, the valence band well is recreated using Al. Strain compensation is unremarkable from its initial position in Figure 2.
Referring to Figure 8, a Indium free device is shown. Indium is removed from the device shown graphed in Figure 6. The quantum well includes GaAsNSb. Device strain is shown to improve with the removal of In.
Referring to Figure 9, nitrogen is shown to be removed from the quantum well for the device shown in Figure 4. The removal of N from the quantum well increases band gap and hole confinement. Strain, however, is also increased in the quantum well, but is compensated for in the barrier region.
Referring to Figure 10, a strain compensated device is illustrated. The device of Figure 8 is improved by adding nitrogen to the barrier layers and aluminum to the confining layers. The quantum well is GaAsSbN. This combination increases the hole well and decreases the electron well. The overall strain in the device is reduced.
Referring to Figure 11 , additional strain compensation is shown by adding phosphorous (P) to the barrier layers. The device in Figure 11 is shown to have AlGaAs confinement layers, and a GaAsSbN quantum well. Indium can also be used in the quantum well.
By normal means it is impossible to reach 1310 nm quantum wells used in datacom VCSELs and edge emitters. Referring to Figure 1 , what is illustrated is a typical InGaAs strained quantum well on GaAs. By using nitrogen for strain compensation in the barriers (fig. 4, 9), enough indium can be added to the quantum wells without relaxation to reach 1310 nm, and because little or no nitrogen is used in the quantum well itself hole confinement and material quality are maintained. Using AlGaAs confining layers with sufficient Al to avoid extra wells being formed is advantageous.
As mentioned above, Figure 8 shows a GaAsSbN quantum well with GaAs barriers. In this case, both Sb and nitrogen lower the band gap. The Sb causes the quantum well to tend towards poor electron confinement with good hole confinement, and the nitrogen tends to go in the opposite direction towards poor hole confinement and good electron confinement. By adjusting the ratio of these at least 0.07 ev well depth in the conduction band, and 0.05 ev depth in the valence band can be achieved while achieving both 1310 nm and 1550 nm light emission.
If large quantities of Sb and little N are used in the quantum wells such that there is excessive compressive strain in the quantum wells, invention aspect 1 can be combined with this to compensate the excessive compressive strain. That is nitrogen or phosphorous can be added to the barriers layers because it tends to deepen the electron well which the Sb in the quantum well tends to shallow the electron well. It is also useful to increase the gap of the confining layers with Al or even P once again to avoid extra wells.
Indium can be used in the quantum well of invention to adjust the wavelength, well depths and strain in the quantum wells. As the band gap shrinks, the wells become more compressive. But adding indium has only a secondary effect on the relative band offsets (valence band or conduction band) as shown in Figures 5 and 6. Fig 6 will work for both 1310 nm and 1550 nm active regions.
As shown in figure 7, AlGaAs barrier layers can be used for InGaAsN quantum wells to increase the hole well depth. Because nitrogen increases the electron effective mass the quantum wells containing nitrogen can be made thinner, that is less than 50 A. In VCSELs, this means there are more quantum wells.
All aspects of the present invention can apply to single as well as multiple quantum wells in both edge emitters and VCSELs and other semiconductor lasers. In all of the above, at least a 0.07 ev well depth is maintained in the conduction band, and a 0.05 ev depth is maintained in the valence band. The lack of steps obtained using 100 or 111 on orientation material makes it easier to grow more highly strained layers without relaxation. Epi flattening techniques, which reduce the bunching of steps, can be used in combination with the above. Intra-quantum well mechanical stabilizers can also be used with the above.
Referring to Figure 12, illustrated is a sectional view of a vertical cavity surface emitting laser 100 (VCSEL). The VCSEL 100 can be grown by techniques such as metal organic molecular beam epitaxy, or metal-organic chemical vapor deposition. Reference is made to U.S. Patent No. 5,903,589, assigned to the assignee for the present invention, which describes methods of VCSEL fabrication use in the art. The VCSEL can preferably be grown on a GaAs substrate 101 due to the robust nature and low cost of the material, however it should be recognized that semiconductor materials, Ge for example, could also be used as the substrate. The VCSEL 100 can then be formed by disposing layers on the substrate.
Epitaxial layers can include: a first mirror stack 105 disposed on the substrate 101 , a first cladding region 108 disposed on the first mirror stack 105, an active region 110 disposed on the first cladding region 108, a second cladding region 112 disposed on the active region 110, and a second mirror stack 115 disposed on the second cladding region 112. The active region 110 can further includes one or more quantum wells 120 being separated from each other by barrier layers 125, depending on the application for which the VCSEL 100 is designed. One of ordinary skill in the art can find it obvious to differ the number of quantum wells 120 in the VCSEL active region 110.
The first mirror stack 105 can be grown by epitaxially depositing mirror pair layers 106 on the substrate 101. In order to crystal lattice match mirror stack 105 to the substrate 101 , a suitable semiconductor material system for the mirrored pairs 106 should be deposited. In this specific example, which shouldn't be taken as a limitation of the full scope of the present invention, the substrate 101 is GaAs, therefore a GaAs/AIGaAs material system can be employed. To achieve a high percentage of reflectivity, the number of mirror pair layers 106 in the stack 105 can usually range from 20 to 40, depending on the difference between the refractive indices of the layers. Different refractive indexes are also achievable by altering the Aluminum content in the mirror stack 105.
A first cladding region 108 can be made of one or more layers epitaxially disposed on the first mirror stack 105. The first cladding region 108 in the currently described embodiment of the invention can be made of a GaAsN material system.
It has been shown that Nitrogen added to the quantum well 120 can have the effect of increasing the strain between the layers, which reduces the band gap energy of the excited state. Band gap energy reduction generally decreases the amount of energy required to excite the material, and increases the wavelength of the emitted photon. This can be desirable to achieve longer wavelength VCSELs 100. The more Nitrogen that is added to the quantum well 120, the greater this reduction in band gap energy can be, and thus longer wavelength VCSELs 100 can be produced.
By using nitrogen in the GaAsN barrier layers and secondarily in the quantum wells themselves, the strain in the structure can be reduced, which can increase the allowable thickness of the quantum wells, and the energy gap can be reduced both which can increases the allowable wavelength. The use of nitrogen in the quantum wells can make the valence band discontinuity nonconfining or type 2. By using AlGaAs or AIGaAsN as the confining material, however, and GaAsN, AlGaAs, or AIGaAsN or GaAsP barrier layers, the nonconfining problem can also be reduced. In addition, if Sb replaces a portion of the As in the quantum well, the type II transition caused by nitrogen can further be avoided allowing even more nitrogen. Because even more nitrogen is allowable, more indium is also allowable. Because nitrogen, indium, and Sb all reduce the band gap energy, the achievable wavelengths extend to wavelengths longer than either 1310nm used for datacom or 1550 nm used for telecom.
By adding Nitrogen to the InGaAs quantum wells, the overall strain in the well can become significantly less allowing more indium before reaching the critical thickness, thus making longer wavelength VCSELs possible. Using nitrogen for strain compensation in the barriers, the allowable strain in the quantum well region can increase meaning even more indium can be used in the quantum wells. More indium is allowable without violating the critical thickness, making for an even lower band gap and longer wavelengths. In addition, using nitrogen in the barrier layers between the quantum wells can also reduce the energy of these barriers in the conduction band making the energy of the quantum state lower, further increasing the allowable wavelength. Using nitrogen in the barrier layers can also be advantageous in avoiding type II behavior in the valence band because as nitrogen is incorporated in the quantum wells, the conduction band discontinuity increases, and the valence band discontinuity decreases. In addition, use of AlGaAs or AIGaAsN for the confining structure can further avoid unintentional wells in the valence band at the barrier layer confining layer boundary. Finally, the use of Sb in the quantum well can reduce the band gap energy further, while avoiding the type II behavior (allowing even more nitrogen). All of these aspects contribute to the ability to create very long wavelength active regions. Introducing Nitrogen into the active region 110 is not generally without drawbacks. GaN and InN can have large differences in their lattice constants as well as optimal growth conditions. Due to this lattice mismatch, the quality of the material can be greatly compromised when layers comprising the active region 110 are grown beyond a certain critical thickness. Layers thicker than this critical thickness can have misfit dislocations, relaxing the strain between the layers, and decreasing the material quality. This can substantially compromises the quality of the VCSEL 100.
By including Nitrogen in the barrier layers 125, the band gap energy decrease can be observed as it is when Nitrogen is added only to the active region 110. However, the amount of Nitrogen that is needed in the active region 110 to achieve a given band gap energy reduction, and therefore a longer wavelength, can be reduced. The lattice mismatch can therefore not generally be as severe as when Nitrogen is added to the active region 110 alone, thus making the material system easier to fabricate. Higher quality VCSELs can be achieved by introducing Nitrogen into the barrier regions125 than when Nitrogen is only added to the active region 110.
Active region 110 can next be epitaxially deposited on the first cladding region 108. The active region 110 can include one or more quantum wells 120. The preferred embodiment uses quantum wells 120 of less than 50 angstroms. When Nitrogen is introduced into the active region 110 or the cladding region 108, 112, the effective electron mass in the regions can increase dramatically. With this increased density of the states, the amount of Indium or Nitrogen needed to produce a given amount of gain in the active region 110 generally decreases. Therefore, the volume of the quantum well 120 can also be decreased, giving less volume for parasitics to occur in. A second cladding region 112 can be made of one or more layers epitaxially disposed on the active region 110. The second cladding region 112 can be made of a GaAsN material system.
A second mirror stack 115 can next be grown by epitaxially depositing mirror pairs layers 116 on the second cladding region 115. In order to crystal lattice match mirror stack 115 to the substrate 101 , a suitable semiconductor material system for the mirrored pairs 116 should be deposited. The substrate 101 is formed of GaAs, therefore a GaAs/AIGaAs material system can be employed. To achieve a high percentage of reflectivity, the number of mirror pair layers 116 in the stack 115 can usually range from 20 to 40, depending on the difference between the refractive indices of the layers. Different refractive indexes are achievable by altering the Aluminum content in the mirror stack 115.
Referring now to Figure 13, an alternate embodiment of the present invention is shown. A flattening layer 235 can be sandwiched between the lower confining layer and the quantum wells. When the various layers are grown on the substrate, bunching of molecular steps form on the surface of the newly formed layers. The steps on the layer's surface increase the likelihood that layers adjacent to the substrate can dislocate from the substrate. A heavily compressively strained InGaAs flattening layer 235 grown before the active region 210 at a distance sufficient to minimize the straining effects on the quantum well layers generally has the effect of flattening the surface to which the active region 210 is disposed. The distance between the flattening layer 235 and the quantum wells can be several hundred angstroms. Growing this flattening layer 235 between the lower confining layer 201 and the first mirror stack 205 flattens out these molecular steps. The surface can be further flattened when the epi layers are grown on "100 or 111 on" orientation substrates. If the substrate is in "off" orientation, the number of molecular steps can increase and the likelihood of bunching of steps increases, thereby increasing the likelihood for dislocation. By flattening the surface that the stacks are deposited on, the strain between layers can be further increased through the addition of greater amounts of In or Sb in the active region. This increased In or Sb generally decreases the band gap energy, thereby making it easier to grow VCSELs 201 that emit longer wavelengths.
Quantum well depth can be an important consideration in achieving optimal gain from VCSEL quantum wells. Comprehensive, up-to-date compilations of band parameters useful for the development of semiconductor devices, such as VCSELS, are generally discussed in a paper entitled "Band parameters for lll-V compound semiconductors and their alloys," by Vurgraftman, Meyer and Ram-Mohan (Journal of Applied Physics, Volume 89, Number 1 1 , 1 June 2001 ). The paper provides some insight for the skilled in the art on calculating band offsets, thereby enabling the achievement of optimal quantum well depth utilizing various materials, and is hereby incorporated by reference into the present disclosure for its teaching.
Quantum wells for VCSELs should be designed in order to promote confinement of carriers within the quantum wells instead of outside of the quantum wells, while at the same time not being so deep as to prohibit adequate flow of carriers between the wells. Proper quantum well depth will maximize the gain in the quantum wells of a VCSEL, which minimizes the threshold current and maximizes slope efficiency (both desirable outcomes). Luminescence and gain within a quantum well is related to the product of holes and electrons within the quantum well. Quantum well depth is established by setting band offsets. Two bands used to determine the quantum well depth are the valence and conduction bands (the valence band associated with hole wells and the conduction band with electron wells). Setting of the bands determines the offsets (meV, mili electron volts) for the quantum well and provides depth associated with the confinement of holes and electrons.
Figures 14-22 provide graphical illustrations of VCSEL behavior at different well depths. Although the simulations illustrated in Figures 14-22 were conducted on AlGaAs quantum wells, the overall analysis is applicable to other materials since temperature will generally be the same and effective masses are not vastly different between devices.
Figures 14-16 are a first group of graphs representing the analysis of a normal set of three quantum wells 1401 for an 850 nm VCSEL under bias (actively lasing). In this case there is substantial p-doping, which suppresses the electron concentration relative to the hole concentration. As shown on the vertical axis of the graph in FIG. 14, well depth of three quantum wells 1401 was established by setting the valence band offsets 1405 at approximately 125 meV and the conduction band offset 1410 at 250 meV. It should be appreciated that the quantum well number does not have to be limited to three. As can be seen within the graphical data in FIG. 15, there is little recombination outside the three quantum wells shown. This can be seen where more electrons 1507 and holes 1509 are found recombining within the quantum wells than the area outside (or in-between) the quantum wells where some holes 1511 and minimal electrons exist. Although enough of both carriers are present, thus enabling sufficient transport between the wells. Referring to FIG. 16, the total recombination 1603 of holes with electrons occurring within the wells, rather than outside the wells 1611 , results in good luminescence and thus good gain for the VCSEL quantum wells.
Figures 17-19 illustrate a second group of graphs representing the analysis of quantum wells under bias. Referring to FIG. 17, quantum well depths were set at approximately 60 meV for valence bands 1703 and 120 meV for conduction bands 1705. Referring to FIG. 18, there is shown an increasing number of holes and electrons 181 1 outside the three quantum wells. Such loss of holes and electrons outside of the quantum wells results in less luminescence 1901 and, therefore, less gain resulting from the quantum wells as shown in FIG. 19
Figures 20-22 are a third group of graphs representing the analysis of quantum wells under bias. The well depths for the three quantum wells were set at approximately 40 meV for valence bands 2003 and 80 meV for conduction bands 2005. As can be seen in FIG. 21 , recombination 2101 outside of the three quantum wells has become quite large. Referring to FIG. 22, loss of recombination within the quantum wells results in a significantly less luminescence 2201 and gain due to undesirable parasitic luminescence 2205.
Based on the foregoing analysis for the quantum wells represented in the three groups, it would be desirable to develop VCSELs having quantum wells hole depths of at least 40 MeV and electron depths of at least 80 MeV. Such a setting for the valence and conduction bands would provide at least minimally acceptable gain; however, optimal quantum well hole well depths have been shown to be up to and including 125 MeV for the Valence bands and conduction bands with a setting of up to and including 250 MeV. Well depths even greater may be acceptable, as long as sufficient transport between the wells is maintained by thermionic emission, tunneling, or both.
The embodiment and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered. The description as set forth is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the spirit and scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects.

Claims

What is claimed is:
1 . A vertical cavity surface emitting laser (VCSEL), comprising:
at least one quantum well having a depth of at least 40 meV and comprised of InGaAsSbN;
barrier layers sandwiching said at least one quantum well; and
confinement layers sandwiching said barrier layers.
2. The VCSEL of claim 1 wherein said barrier layers are comprised of GaAsP.
3. The VCSEL of claim 1 wherein said confinement layers are further comprised of AlGaAs.
4. The VCSEL of claim 2 wherein said confinement layers are further comprised of AlGaAs.
5. The VCSEL of claim 3 wherein said barrier layers are further comprised of AlGaAs.
6. The VCSEL of claim 1 wherein said barrier layers are comprised of
AlGaAs.
7. The VCSEL of claim 1 wherein said at least one quantum well further comprises >1 % N added to the quantum well(s).
8. The VCSEL of claim 7 wherein said barrier layers are comprised of GaAsP.
9. The VCSEL of claim 7 wherein said confinement layers are comprised of AlGaAs.
10. The VCSEL of claim 8 wherein said confinement layers are comprised of AlGaAs.
1 1 . The VCSEL of claim 7 wherein said barrier layers are comprised of
AlGaAs.
12. The VCSEL of claim 9 wherein said barrier layers are comprised of AlGaAs.
13. The VCSEL of claim 1 wherein said quantum well is up to and including 50 A in thickness.
14. The VCSEL of claim 13 wherein said barrier layers are comprised of GaAsP.
15. The VCSEL of claim 13 wherein said confinement layers are further comprised of AlGaAs.
16. The VCSEL of claim 14 wherein said confinement layers are further comprised of AlGaAs.
17. The VCSEL of claim 15 wherein said barrier layers are further comprised of AlGaAs.
18. The VCSEL of claim 13 wherein said barrier layers are comprised of AlGaAs.
19. The VCSEL of claim 13 wherein said at least one quantum well further comprises >1 % N added to the quantum well(s).
20. The VCSEL of claim 19 wherein said barrier layers are comprised of GaAsP.
21. The VCSEL of claim 19 wherein said confinement layers are comprised of AlGaAs.
22. The VCSEL of claim 20 wherein said confinement layers are comprised of AlGaAs.
23. The VCSEL of claim 19 wherein said barrier layers are comprised of AlGaAs.
24. The VCSEL of claim 21 wherein said barrier layers are comprised of AlGaAs.
25. A vertical cavity surface emitting laser (VCSEL), comprising: at least one quantum well having a depth of at least 40 meV and comprised of InGaAsSbN;
barrier layers sandwiching said at least one quantum well; and
AlGaAs confinement layers sandwiching said barrier layers.
26. The VCSEL of claim 1 wherein said barrier layers are comprised of GaAsP.
27. The VCSEL of claim 3 wherein said barrier layers are comprised of AlGaAs.
28. The VCSEL of claim 1 wherein said barrier layers are comprised of AlGaAs.
29. The VCSEL of claim 13 wherein said at least one quantum well further comprises >1% N added to the quantum well(s).
30. The VCSEL of claim 17 wherein said barrier layers are comprised of GaAsP.
31. The VCSEL of claim 17 wherein said barrier layers are comprised of AlGaAs.
32. The VCSEL of claim 25 wherein said quantum well is up to and including 50 A in thickness.
33. A vertical cavity surface emitting laser (VCSEL), comprising:
at least one quantum well having a depth of at least 40 meV and comprised of InGaAsSbN;
AlGaAs barrier layers sandwiching said at least one quantum well; and
AlGaAs confinement layers sandwiching said barrier layers.
34. The VCSEL of claim 33 wherein said quantum well is up to and including 50 A in thickness.
PCT/US2002/041736 2001-12-20 2002-12-13 Vertical cavity surface emitting laser including indium, antimony and nitrogen in the active region WO2003054353A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US10/026,016 US7095770B2 (en) 2001-12-20 2001-12-20 Vertical cavity surface emitting laser including indium, antimony and nitrogen in the active region
US10/026,016 2001-12-20

Publications (2)

Publication Number Publication Date
WO2003054353A2 true WO2003054353A2 (en) 2003-07-03
WO2003054353A3 WO2003054353A3 (en) 2004-03-18

Family

ID=21829365

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2002/041736 WO2003054353A2 (en) 2001-12-20 2002-12-13 Vertical cavity surface emitting laser including indium, antimony and nitrogen in the active region

Country Status (3)

Country Link
US (1) US7095770B2 (en)
TW (1) TWI236197B (en)
WO (1) WO2003054353A2 (en)

Families Citing this family (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3735047B2 (en) * 2000-07-31 2006-01-11 古河電気工業株式会社 Semiconductor laser device and manufacturing method thereof
US7295586B2 (en) * 2002-02-21 2007-11-13 Finisar Corporation Carbon doped GaAsSb suitable for use in tunnel junctions of long-wavelength VCSELs
US6822995B2 (en) 2002-02-21 2004-11-23 Finisar Corporation GaAs/AI(Ga)As distributed bragg reflector on InP
US7860137B2 (en) 2004-10-01 2010-12-28 Finisar Corporation Vertical cavity surface emitting laser with undoped top mirror
CN101432936B (en) 2004-10-01 2011-02-02 菲尼萨公司 Vertical cavity surface emitting laser having multiple top-side contacts
US8069206B2 (en) * 2005-03-18 2011-11-29 Clearone Communications, Inc. System and method for real-time feedback with conservative network usage in a teleconferencing system
US7736382B2 (en) 2005-09-09 2010-06-15 Lockheed Martin Corporation Apparatus for optical stimulation of nerves and other animal tissue
US8792978B2 (en) 2010-05-28 2014-07-29 Lockheed Martin Corporation Laser-based nerve stimulators for, E.G., hearing restoration in cochlear prostheses and method
US8945197B1 (en) 2005-10-24 2015-02-03 Lockheed Martin Corporation Sight-restoring visual prosthetic and method using infrared nerve-stimulation light
US8475506B1 (en) 2007-08-13 2013-07-02 Lockheed Martin Corporation VCSEL array stimulator apparatus and method for light stimulation of bodily tissues
US8956396B1 (en) 2005-10-24 2015-02-17 Lockheed Martin Corporation Eye-tracking visual prosthetic and method
US8929973B1 (en) 2005-10-24 2015-01-06 Lockheed Martin Corporation Apparatus and method for characterizing optical sources used with human and animal tissues
US20080077200A1 (en) 2006-09-21 2008-03-27 Aculight Corporation Apparatus and method for stimulation of nerves and automated control of surgical instruments
US8709078B1 (en) 2011-08-03 2014-04-29 Lockheed Martin Corporation Ocular implant with substantially constant retinal spacing for transmission of nerve-stimulation light
US8012189B1 (en) 2007-01-11 2011-09-06 Lockheed Martin Corporation Method and vestibular implant using optical stimulation of nerves
US8744570B2 (en) * 2009-01-23 2014-06-03 Lockheed Martin Corporation Optical stimulation of the brainstem and/or midbrain, including auditory areas
US8996131B1 (en) 2006-09-28 2015-03-31 Lockheed Martin Corporation Apparatus and method for managing chronic pain with infrared light sources and heat
US8498699B2 (en) 2008-10-03 2013-07-30 Lockheed Martin Company Method and nerve stimulator using simultaneous electrical and optical signals
US7883536B1 (en) 2007-01-19 2011-02-08 Lockheed Martin Corporation Hybrid optical-electrical probes
US8840654B2 (en) 2011-07-22 2014-09-23 Lockheed Martin Corporation Cochlear implant using optical stimulation with encoded information designed to limit heating effects
WO2010040142A1 (en) 2008-10-03 2010-04-08 Lockheed Martin Corporation Nerve stimulator and method using simultaneous electrical and optical signals
US20210257809A1 (en) * 2017-11-22 2021-08-19 Iqe Plc Strain-balanced semiconductor structure

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5960018A (en) * 1996-09-25 1999-09-28 Picolight Incorporated Extended wavelength strained layer lasers having strain compensated layers

Family Cites Families (90)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5726492A (en) 1980-07-24 1982-02-12 Nec Corp Semiconductor laser
US4445218A (en) 1981-09-28 1984-04-24 Bell Telephone Laboratories, Incorporated Semiconductor laser with conductive current mask
US4608697A (en) 1983-04-11 1986-08-26 At&T Bell Laboratories Spectral control arrangement for coupled cavity laser
US4622672A (en) 1984-01-20 1986-11-11 At&T Bell Laboratories Self-stabilized semiconductor lasers
US4829347A (en) 1987-02-06 1989-05-09 American Telephone And Telegraph Company, At&T Bell Laboratories Process for making indium gallium arsenide devices
JPS6461081A (en) 1987-09-01 1989-03-08 Japan Res Dev Corp Distributed-feedback type semiconductor laser and manufacture thereof
US4896325A (en) 1988-08-23 1990-01-23 The Regents Of The University Of California Multi-section tunable laser with differing multi-element mirrors
US4873696A (en) 1988-10-31 1989-10-10 The Regents Of The University Of California Surface-emitting lasers with periodic gain and a parallel driven nipi structure
US5082799A (en) 1990-09-14 1992-01-21 Gte Laboratories Incorporated Method for fabricating indium phosphide/indium gallium arsenide phosphide buried heterostructure semiconductor lasers
US5245622A (en) 1992-05-07 1993-09-14 Bandgap Technology Corporation Vertical-cavity surface-emitting lasers with intra-cavity structures
US5251225A (en) * 1992-05-08 1993-10-05 Massachusetts Institute Of Technology Quantum-well diode laser
US5293392A (en) 1992-07-31 1994-03-08 Motorola, Inc. Top emitting VCSEL with etch stop layer
JP2783086B2 (en) 1992-09-25 1998-08-06 日本電気株式会社 Semiconductor laser device and optical connection device
US5343487A (en) 1992-10-01 1994-08-30 Optical Concepts, Inc. Electrical pumping scheme for vertical-cavity surface-emitting lasers
US5568504A (en) 1992-12-03 1996-10-22 Siemens Aktiengesellschaft Surface-emitting laser diode
US5416044A (en) 1993-03-12 1995-05-16 Matsushita Electric Industrial Co., Ltd. Method for producing a surface-emitting laser
JP3207590B2 (en) 1993-03-15 2001-09-10 富士通株式会社 Optical semiconductor device
JP3135185B2 (en) 1993-03-19 2001-02-13 三菱電機株式会社 Semiconductor etching solution, semiconductor etching method, and method for determining GaAs surface
JP3362356B2 (en) * 1993-03-23 2003-01-07 富士通株式会社 Optical semiconductor device
US5358880A (en) 1993-04-12 1994-10-25 Motorola, Inc. Method of manufacturing closed cavity LED
US5456205A (en) 1993-06-01 1995-10-10 Midwest Research Institute System for monitoring the growth of crystalline films on stationary substrates
US5383211A (en) * 1993-11-02 1995-01-17 Xerox Corporation TM-polarized laser emitter using III-V alloy with nitrogen
US5422901A (en) 1993-11-15 1995-06-06 Motorola, Inc. Semiconductor device with high heat conductivity
US5491710A (en) 1994-05-05 1996-02-13 Cornell Research Foundation, Inc. Strain-compensated multiple quantum well laser structures
US5480813A (en) 1994-06-21 1996-01-02 At&T Corp. Accurate in-situ lattice matching by reflection high energy electron diffraction
AU4695096A (en) * 1995-01-06 1996-07-24 National Aeronautics And Space Administration - Nasa Minority carrier device
US5513204A (en) 1995-04-12 1996-04-30 Optical Concepts, Inc. Long wavelength, vertical cavity surface emitting laser with vertically integrated optical pump
JPH08293489A (en) 1995-04-25 1996-11-05 Sharp Corp Method of dry etching gallium nitride based compound semiconductor
JP3691544B2 (en) 1995-04-28 2005-09-07 アジレント・テクノロジーズ・インク Manufacturing method of surface emitting laser
FR2739230B1 (en) 1995-09-22 1997-12-19 Oudar Jean Louis VERTICAL CAVITY LASER EMISSION COMPONENT WITH SURFACE EMISSION AT A WAVELENGTH BETWEEN 1.3 AND 1.5 MU M AND PROCESS FOR ITS REALIZATION
EP0852834B1 (en) 1995-09-29 1999-03-31 BRITISH TELECOMMUNICATIONS public limited company Optically resonant structure
US5757833A (en) * 1995-11-06 1998-05-26 The Furukawa Electric Co., Ltd. Semiconductor laser having a transparent light emitting section, and a process of producing the same
US5719891A (en) 1995-12-18 1998-02-17 Picolight Incorporated Conductive element with lateral oxidation barrier
DE69610610T2 (en) 1995-12-26 2001-05-03 Nippon Telegraph & Telephone Vertical cavity surface emitting laser and method of manufacturing the same
FR2743195B1 (en) 1995-12-27 1998-02-06 Alsthom Cge Alcatel SURFACE EMITTING SEMICONDUCTOR LASER
FR2743196B1 (en) 1995-12-27 1998-02-06 Alsthom Cge Alcatel METHOD FOR MANUFACTURING A SURFACE EMITTING SEMICONDUCTOR LASER
US5912913A (en) 1995-12-27 1999-06-15 Hitachi, Ltd. Vertical cavity surface emitting laser, optical transmitter-receiver module using the laser, and parallel processing system using the laser
JP3428797B2 (en) * 1996-02-08 2003-07-22 古河電気工業株式会社 Semiconductor laser device
US5754578A (en) 1996-06-24 1998-05-19 W. L. Gore & Associates, Inc. 1250-1650 nm vertical cavity surface emitting laser pumped by a 700-1050 nm vertical cavity surface emitting laser
US5805624A (en) 1996-07-30 1998-09-08 Hewlett-Packard Company Long-wavelength infra-red vertical cavity surface-emitting laser on a gallium arsenide substrate
WO1998007218A1 (en) 1996-08-09 1998-02-19 W.L. Gore & Associates, Inc. Vertical cavity surface emitting laser with tunnel junction
US5724374A (en) 1996-08-19 1998-03-03 Picolight Incorporated Aperture comprising an oxidized region and a semiconductor material
JP3788831B2 (en) 1996-08-30 2006-06-21 株式会社リコー Semiconductor device and manufacturing method thereof
FR2753577B1 (en) 1996-09-13 1999-01-08 Alsthom Cge Alcatel METHOD FOR MANUFACTURING A SEMICONDUCTOR OPTOELECTRONIC COMPONENT AND COMPONENT AND MATRIX OF COMPONENTS MANUFACTURED ACCORDING TO THIS METHOD
US5719894A (en) 1996-09-25 1998-02-17 Picolight Incorporated Extended wavelength strained layer lasers having nitrogen disposed therein
US5719895A (en) 1996-09-25 1998-02-17 Picolight Incorporated Extended wavelength strained layer lasers having short period superlattices
JP3854693B2 (en) * 1996-09-30 2006-12-06 キヤノン株式会社 Manufacturing method of semiconductor laser
JPH10173294A (en) 1996-10-07 1998-06-26 Canon Inc Multilayered compound semiconductor film mirror containing nitrogen and surface type light emitting device
US5877038A (en) 1996-11-27 1999-03-02 The Regents Of The University Of California Method of making a vertical cavity laser
US5732103A (en) 1996-12-09 1998-03-24 Motorola, Inc. Long wavelength VCSEL
US5883912A (en) 1996-12-09 1999-03-16 Motorola, Inc. Long wavelength VCSEL
US5835521A (en) 1997-02-10 1998-11-10 Motorola, Inc. Long wavelength light emitting vertical cavity surface emitting laser and method of fabrication
US5815524A (en) 1997-02-25 1998-09-29 Motorola, Inc. VCSEL including GaTlP active region
US5898722A (en) 1997-03-10 1999-04-27 Motorola, Inc. Dual wavelength monolithically integrated vertical cavity surface emitting lasers and method of fabrication
EP0865124B1 (en) 1997-03-12 2003-01-22 BRITISH TELECOMMUNICATIONS public limited company Mirrors for VCSEL
FR2761822B1 (en) 1997-04-03 1999-05-07 Alsthom Cge Alcatel SEMICONDUCTOR LASER WITH SURFACE EMISSION
US5943359A (en) 1997-04-23 1999-08-24 Motorola, Inc. Long wavelength VCSEL
US5903586A (en) * 1997-07-30 1999-05-11 Motorola, Inc. Long wavelength vertical cavity surface emitting laser
US5978398A (en) 1997-07-31 1999-11-02 Motorola, Inc. Long wavelength vertical cavity surface emitting laser
US5956363A (en) 1997-08-15 1999-09-21 Motorola, Inc. Long wavelength vertical cavity surface emitting laser with oxidation layers and method of fabrication
US5943357A (en) 1997-08-18 1999-08-24 Motorola, Inc. Long wavelength vertical cavity surface emitting laser with photodetector for automatic power control and method of fabrication
US6061380A (en) 1997-09-15 2000-05-09 Motorola, Inc. Vertical cavity surface emitting laser with doped active region and method of fabrication
US6021147A (en) 1997-11-04 2000-02-01 Motorola, Inc. Vertical cavity surface emitting laser for high power single mode operation and method of fabrication
US6148016A (en) 1997-11-06 2000-11-14 The Regents Of The University Of California Integrated semiconductor lasers and photodetectors
US5991326A (en) 1998-04-14 1999-11-23 Bandwidth9, Inc. Lattice-relaxed verticle optical cavities
US6228670B1 (en) * 1998-04-23 2001-05-08 Nec Corporation Method of manufacturing a semiconductor optical waveguide array and an array-structured semiconductor optical device
US6195381B1 (en) * 1998-04-27 2001-02-27 Wisconsin Alumni Research Foundation Narrow spectral width high-power distributed feedback semiconductor lasers
JP3189791B2 (en) 1998-06-19 2001-07-16 日本電気株式会社 Semiconductor laser
US6207973B1 (en) 1998-08-19 2001-03-27 Ricoh Company, Ltd. Light emitting devices with layered III-V semiconductor structures
US6195485B1 (en) 1998-10-26 2001-02-27 The Regents Of The University Of California Direct-coupled multimode WDM optical data links with monolithically-integrated multiple-channel VCSEL and photodetector
US6314118B1 (en) 1998-11-05 2001-11-06 Gore Enterprise Holdings, Inc. Semiconductor device with aligned oxide apertures and contact to an intervening layer
KR20010089540A (en) 1998-12-03 2001-10-06 추후보정 Compound semiconductor structures for optoelectronic devices
US6603784B1 (en) 1998-12-21 2003-08-05 Honeywell International Inc. Mechanical stabilization of lattice mismatched quantum wells
DE60012704T2 (en) 1999-03-01 2005-01-13 The Regents Of The University Of California, Oakland TUNABLE LASER WITH AN INTEGRATED WAVELENGTH MONITORING DEVICE AND ASSOCIATED OPERATING METHOD
US6252896B1 (en) 1999-03-05 2001-06-26 Agilent Technologies, Inc. Long-Wavelength VCSEL using buried bragg reflectors
AU5866300A (en) 1999-04-27 2000-11-10 Gore Enterprise Holdings, Inc. Postgrowth adjustment of cavity spectrum for semiconductor lasers and detectors
US6341137B1 (en) 1999-04-27 2002-01-22 Gore Enterprise Holdings, Inc. Wavelength division multiplexed array of long-wavelength vertical cavity lasers
US6349106B1 (en) 1999-09-02 2002-02-19 Agility Communications, Inc. Method for converting an optical wavelength using a monolithic wavelength converter assembly
WO2001017076A2 (en) 1999-09-02 2001-03-08 Agility Communications, Inc. Tunable laser source with integrated optical amplifier
US6424669B1 (en) 1999-10-29 2002-07-23 E20 Communications, Inc. Integrated optically pumped vertical cavity surface emitting laser
US6714572B2 (en) 1999-12-01 2004-03-30 The Regents Of The University Of California Tapered air apertures for thermally robust vertical cavity laser structures
WO2002017448A1 (en) 2000-08-22 2002-02-28 Regents Of The University Of California, The Distributed bragg reflectors incorporating sb material for long-wavelength vertical cavity surface emitting lasers
AU2001290893A1 (en) 2000-09-15 2002-03-26 Regents Of The University Of California Oxide and air apertures and method of manufacture
US6542530B1 (en) 2000-10-27 2003-04-01 Chan-Long Shieh Electrically pumped long-wavelength VCSEL and methods of fabrication
US20020075920A1 (en) 2000-12-15 2002-06-20 Sylvia Spruytte Laser diode device with nitrogen incorporating barrier
US6434180B1 (en) 2000-12-19 2002-08-13 Lucent Technologies Inc. Vertical cavity surface emitting laser (VCSEL)
US6362069B1 (en) 2000-12-28 2002-03-26 The Trustees Of Princeton University Long-wavelength VCSELs and method of manufacturing same
US20020131462A1 (en) 2001-03-15 2002-09-19 Chao-Kun Lin Intracavity contacted long wavelength VCSELs with buried antimony layers
DE60107679T2 (en) 2001-09-18 2005-12-15 Avalon Photonics Ag Indium phosphide-based vertical cavity surface emitting laser
US6647050B2 (en) 2001-09-18 2003-11-11 Agilent Technologies, Inc. Flip-chip assembly for optically-pumped lasers

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5960018A (en) * 1996-09-25 1999-09-28 Picolight Incorporated Extended wavelength strained layer lasers having strain compensated layers

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
SHIMIZU H ET AL: "HIGH-PERFORMANCE CW 1.26-MUM GAINASSB-SQW RIDGE LASERS" IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, IEEE SERVICE CENTER, US, vol. 7, no. 2, March 2001 (2001-03), pages 355-364, XP001108226 ISSN: 1077-260X *
YANG X ET AL: "HIGH-TEMPERATURE CHARACTERISTICS OF 1.3 MUM INGAASN:SB/GAAS MULTIPLE-QUANTUM-WELL LASERS GROWN BY MOLECULAR-BEAM EPITAXY" APPLIED PHYSICS LETTERS, AMERICAN INSTITUTE OF PHYSICS. NEW YORK, US, vol. 76, no. 7, 14 February 2000 (2000-02-14), pages 795-797, XP000934689 ISSN: 0003-6951 *

Also Published As

Publication number Publication date
WO2003054353A3 (en) 2004-03-18
TWI236197B (en) 2005-07-11
US20030118067A1 (en) 2003-06-26
US7095770B2 (en) 2006-08-22
TW200303106A (en) 2003-08-16

Similar Documents

Publication Publication Date Title
US7095770B2 (en) Vertical cavity surface emitting laser including indium, antimony and nitrogen in the active region
JP3504742B2 (en) Laser diode
US6597017B1 (en) Semiconductor device, surface emitting semiconductor laser and edge emitting semiconductor laser
EP1145395B1 (en) Compound semiconductor structures for optoelectronic devices
US8073029B2 (en) Semiconductor optical device
US7286585B2 (en) Low temperature grown layers with migration enhanced epitaxy adjacent to an InGaAsN(Sb) based active region
US7847310B2 (en) Migration enhanced epitaxy fabrication of active regions having quantum wells
US7378680B2 (en) Migration enhanced epitaxy fabrication of quantum wells
US6975660B2 (en) Vertical cavity surface emitting laser including indium and antimony in the active region
US7058112B2 (en) Indium free vertical cavity surface emitting laser
EP1553670B1 (en) Semiconductor device having a quantum well structure including dual barrier layers, semiconductor laser employing the semiconductor device and methods of manufacturing the semiconductor device and the semiconductor laser.
JPH09510831A (en) Quantum layer structure
US6858519B2 (en) Atomic hydrogen as a surfactant in production of highly strained InGaAs, InGaAsN, InGaAsNSb, and/or GaAsNSb quantum wells
JP4045639B2 (en) Semiconductor laser and semiconductor light emitting device
US6922426B2 (en) Vertical cavity surface emitting laser including indium in the active region
US7257143B2 (en) Multicomponent barrier layers in quantum well active regions to enhance confinement and speed
US6859474B1 (en) Long wavelength pseudomorphic InGaNPAsSb type-I and type-II active layers for the gaas material system
US7167495B2 (en) Use of GaAs extended barrier layers between active regions containing nitrogen and AlGaAs confining layers
US7408964B2 (en) Vertical cavity surface emitting laser including indium and nitrogen in the active region
JP4957355B2 (en) Semiconductor light emitting device

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): CA CN JP KR

AL Designated countries for regional patents

Kind code of ref document: A2

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE TR

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: JP

WWW Wipo information: withdrawn in national office

Country of ref document: JP