US20080014670A1 - Semiconductor laser element - Google Patents
Semiconductor laser element Download PDFInfo
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- US20080014670A1 US20080014670A1 US11/851,964 US85196407A US2008014670A1 US 20080014670 A1 US20080014670 A1 US 20080014670A1 US 85196407 A US85196407 A US 85196407A US 2008014670 A1 US2008014670 A1 US 2008014670A1
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- 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
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- B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
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- H01S5/162—Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface with window regions made by diffusion or disordening of the active layer
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- H01S5/164—Window-type lasers, i.e. with a region of non-absorbing material between the active region and the reflecting surface with window regions comprising semiconductor material with a wider bandgap than the active layer
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- H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
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Definitions
- the present invention relates to a semiconductor laser element, and particularly, to a semiconductor laser element used as a light source for an information recording apparatus.
- a recording density in an optical disk for information recording has been increasingly raised because of development in digital information technology, and a high power capability has been simultaneously required in a semiconductor laser element, which is a light source for an information recording apparatus, because of improvement on an information recording speed onto an optical disk. It is unpreferable, however, to cause nonlinearity between a current and an optical output, such as a kink, in usage of the semiconductor laser element, and it is required to provide a semiconductor laser element that has no kink in high power state, in other words with a high kink level.
- a semiconductor laser element In order to improve a recording speed, a semiconductor laser element is effective that has a lens system guiding light from a semiconductor laser element to an optical disk and a low aspect characteristic (a ratio of a vertical spread angle FFPy to a horizontal spread angle FFPx, FFPy/FFPx is small), with which a high optical coupling efficiency can be obtained.
- Japanese Non-examined Patent Publication No. 2-178988 is referred herein.
- an FFPx is made larger in order to obtain a low aspect
- light in a horizontal plane is required to be confined at a higher degree, wherein with confinement of light at a higher degree, inhomogeneity in carrier injection arises due to spatial hole burning, leading to generation of a kink.
- a semiconductor laser element related to the present invention has a ridge structure in which an active layer is provided between a semiconductor layer of one conductivity type and a semiconductor layer of the other conductivity type having a ridge, and window regions that are non-gain regions are provided at both ends thereof, wherein a difference in equivalent refractive index between the ridge and portions on both sides thereof in each of the window regions is larger than a difference in equivalent refractive index between the ridge and portions on both sides thereof in a gain region.
- the semiconductor laser element related to the present invention with such a construction can realize a low aspect ratio without lowering a kink level.
- FIG. 1 is a sectional view of a semiconductor laser diode of a first embodiment related to the present invention in parallel to a resonance direction thereof.
- FIG. 2A is a sectional view taken on line A-A′ of FIG. 1 in a window region of the semiconductor laser diode of a first embodiment and FIG. 2B is a sectional view taken on line B-B′ of FIG. 1 in a gain region of the semiconductor laser diode thereof.
- FIG. 3 is a perspective view of a semiconductor laser element in process of the first embodiment after semiconductor layers are grown in a fabrication process therefor.
- FIG. 4 is a perspective view of a semiconductor laser element in process of the first embodiment after a contact layer is etched in the fabrication process therefor.
- FIG. 5 is a perspective view of a semiconductor laser element in process of the first embodiment after the first etching for forming a ridge ends in the fabrication process therefor.
- FIG. 6 is a perspective view of a semiconductor laser element in process of the first embodiment after the second etching for forming a ridge ends in the fabrication process therefor.
- FIG. 7A is a sectional view in a window region of a semiconductor laser diode related to an example modification of the first embodiment and FIG. 7B is a sectional view in a gain region of the semiconductor laser diode related to the example modification thereof.
- FIG. 8 is a perspective view of a semiconductor laser diode of a second embodiment.
- FIG. 9A is a sectional view in a window region of a semiconductor laser diode of a third embodiment and FIG. 9B is a sectional view in a gain region of the semiconductor laser diode thereof.
- FIG. 10 is a sectional view in a window region of a semiconductor laser diode related to an example modification of the third embodiment.
- FIG. 11 is a sectional view in a window region of a semiconductor laser diode of a fourth embodiment.
- FIG. 12A is a sectional view in a window region of a semiconductor laser diode of a sixth embodiment and FIG. 12B is a sectional view in a gain region of the semiconductor laser diode thereof.
- FIG. 13 is a sectional view of a semiconductor laser diode of a seventh embodiment related to the present invention in parallel to a resonance direction thereof.
- FIG. 14A is a sectional view in a window region of the semiconductor laser diode of a seventh embodiment and FIG. 14B is a sectional view in a gain region of the semiconductor laser diode thereof.
- a semiconductor laser diode of the first embodiment related to the present invention is a ridge type semiconductor laser diode as shown in FIGS. 2A and 2B and has a structure in which a ridge 9 is formed so that part of upper cladding layer are left behind on an active layer 3 on both sides of the ridge 9 , and widow regions 11 , which are non-gain regions for preventing an optical damage, are formed at both ends ( FIG. 1 ).
- the left upper cladding layer 4 a of the window regions 11 are formed so as to be thinner than the left upper cladding layer 4 b of a gain region 10 .
- an equivalent refractive index difference ⁇ n11 in the non-gain regions, each of which is a window region can be larger than an equivalent refractive index difference ⁇ n10 in the gain region, an FFPx can be made large, thereby enabling a low aspect to be obtained.
- a window region 11 in which the left upper cladding layer 4 a is thin in thickness in order to increase the equivalent refractive index difference ⁇ n11 is a non-gain region having no gain or a small gain; therefore, no chance to lower a kink level is encountered even with a light confinement at a great degree.
- the semiconductor laser element of the first embodiment can realize a low aspect without lowering a kink level.
- epitaxially grown on a semiconductor substrate 1 are a lower cladding layer 2 , a multiple quantum well active layer 3 , a first left upper cladding layer 41 , an etching stopper layer ESL 1 , a second left upper cladding layer 42 , an etching stopper layer ESL 2 , an upper cladding layer 43 and a contact layer 6 in the order ( FIG. 3 ).
- Example materials of the substrate and the semiconductor layers are given in Table 1 in a case where a 660 nm semiconductor laser diode for DVD is constructed.
- TABLE 1 Semiconductor substrate 1 n type GaAs substrate Lower cladding layer 2 n type (Al 0.7 Ga 0.3 ) 0.5 In 0.49 P
- Multiple quantum well active active layer constituted of an undoped layer 3 Ga 0.44 In 0.56 P well layer and an undoped (Al 0.5 Ga 0.5 ) 0.51 In 0.49 P barrier layer
- the upper cladding layer indicates the first left upper cladding layer 41 , the second left upper cladding layer 42 and the upper cladding layer 43 .
- etching stopper layers ESL 1 and ESL 2 can be used as the etching stopper layers ESL 1 and ESL 2 .
- example materials for constituting a 780 nm semiconductor laser diode for CD are presented in Table 2.
- Table 2 semiconductor substrate 1 n type GaAs substrate lower cladding layer 2 n type Al 0.48 Ga 0.52 As multiple quantum well active active layer constituted of an undoped layer 3 Al 0.11 Ga 0.89 As well layer and an undoped Al 0.34 Ga 0.66 As barrier layer upper cladding layer p type Al 0.48 Ga 0.52 As layer contact layer 6 p type GaAs layer
- the upper cladding layer indicates the first left upper cladding layer 41 , the second left upper cladding layer 42 and the upper cladding layer 43 .
- Si, proton or Zn can be used as an impurity to form the window regions 11 .
- an impurity is doped into portions of the regions A serving as the window regions so as to cross over the active layer by means of ion implantation, diffusion or the like. With such doping applied, the band gap of the doped active layer increases to form the window regions 11 with no absorption of light.
- the window regions 11 are non-gain regions with neither light absorption nor light amplification.
- the window regions 11 are each formed in a end portion of a width of from 5 ⁇ m to 50 ⁇ m and, more preferably, from 20 ⁇ m to 30 ⁇ m inward from an edge surface.
- the contact layer 6 is entirely or partially etched in the regions A serving as the window regions 11 ( FIG. 4 ).
- a protective film R 1 for providing a ridge is formed and both sides of the protective film R 1 are dry etched ( FIG. 5 ).
- etching conditions are set so that in the regions A, the second left cladding layer 42 is etched partway therein, while in the region B for forming the gain region, the upper cladding layer 43 is etched partway therein.
- a surface level difference in height between the regions A and the region B formed on both sides of the ridge is equal to a surface level difference in height between the regions A and the region B formed by etching the contact layer 6 , which is described using FIG. 4 .
- FIG. 7A is a sectional view of a window region
- FIG. 7B is a sectional view of the gain region.
- a semiconductor laser element of the second embodiment related to the present invention is constructed in a similar manner to that in the first embodiment with the exceptions described below ( FIG. 8 ).
- a left upper cladding layer 4 c with the same thickness is formed across a gain region 10 including window regions 11 on active layer on both sides of a ridge.
- a current blocking layer (buried layer) 21 is formed only on both sides of the ridge in the gain region 10 .
- an equivalent refractive index difference ⁇ n11 between the ridge and portions on both sides thereof in non-gain regions (window regions) can be larger than an equivalent refractive index difference ⁇ n10 between the ridge and portions on both sides thereof in the gain region 10 .
- an FFPx can be large to thereby obtain a low aspect and since the window regions larger in equivalent refractive index difference ⁇ n11 are non-gain regions, no reduction in kink level occurs even in light confinement at a higher degree.
- a semiconductor laser element of the third embodiment related to the present invention is constructed in a similar manner to that in the second embodiment except that formed on both sides of a ridge in window regions 11 is a buried layer 21 a made of a semiconductor material having a refractive index smaller than the current blocking layer 21 formed on both sides of the ridge in a gain region 10 ( FIGS. 9A and 9B ).
- FIGS. 9A and 9B like symbols are attached to constituents similar to those in the first or second embodiment.
- an equivalent refractive index difference ⁇ n11 between the ridge and portions on both sides thereof in non-gain regions (window regions) can be larger than an equivalent refractive index difference ⁇ n10 between the ridge and portions on both sides thereof in the gain region 10 .
- an FFPx can be large to thereby obtain a low aspect and since the window regions larger in equivalent refractive index difference ⁇ n11 are non-gain regions, no reduction in kink level occurs even in light confinement at a higher degree.
- the buried layer 21 a made of a semiconductor material having a refractive index smaller than the current blocking layer 21 is formed on both sides of the ridge in the window regions 11
- another construction may be adopted in which a buried layer made of a similar semiconductor material is formed on both sides of the ridge in the window region 11 and on both sides of the ridge in the gain region 10 with the exception that a carrier concentration in the buried layer on both sides of the ridge in the window regions 11 is higher than that in the buried layer on both sides of the ridge in the gain region 10 , so that the buried layer in the window regions 11 is a high carrier concentration buried layer 21 b ( FIG. 10 ).
- a refractive index of the high carrier concentration buried layer 21 b can be rendered small due to a plasma effect, thereby enabling an action and effect similar to those in the third embodiment to be obtained.
- a semiconductor laser element of the fourth embodiment related to the present invention is constructed such that current blocking layer 21 c is formed using a material absorbing laser oscillated light, for example GaAs on both sides of a ridge in window regions 11 .
- a construction of a gain region 10 may be similar to that in the first embodiment or in the second embodiment (in FIG. 11 , the construction is depicted as being similar to that in the second embodiment).
- a far field pattern (FFPx) in a horizontal plane can be enlarged due to a diffraction phenomenon of light, thereby enabling a low aspect to be realized without lowering a kink level.
- the fifth embodiment related to the present invention is a process in which the left upper cladding layer 4 a in the window regions 11 is formed to be thinner than the left upper cladding layer 4 b in the gain region 10 , which is different from the process described in the first embodiment.
- this fabrication process is different from the process described in the first embodiment in that the etching stopper layer ESL 2 is a multiple quantum well structure and no etching stopper layer ESL 1 is formed. That is, in this process, the first left upper cladding layer 41 and the second left upper cladding layer 42 are formed continuously with the same material.
- the etching stopper layer ESL 2 of a multiple quantum well structure can be a multiple quantum well structure constructed of a Ga 0.58 In 0.42 P well layer and an (Al 0.5 Ga 0.5 ) 0.5 In 0.49 P barrier layer.
- an impurity is, in a similar manner to that in the first embodiment, doped in the regions A used for forming window regions by means of ion implantation, diffusion or the like.
- the etching stopper layer ESL 2 of a multiple quantum well structure in the window regions are degenerated into disorder and loses an etching stopper function.
- etching is conducted for forming the ridge, whereby in the window regions, etching progresses beyond the etching stopper layer ESL 2 , while in the gain region, etching is stopped by the etching stopper layer ESL 2 .
- a thickness of the left upper cladding layer 4 a in the window regions 11 can be thinner than that of the left upper cladding layer 4 b in the gain region 10 with ease.
- the sixth embodiment related to the present invention is a fabrication process fabricating an element having a structure shown in the first embodiment without forming an etching stopper layer.
- a left upper cladding layer 4 e with the same thickness is formed across the gain region 10 including the window regions 11 on both sides of the ridge 9 in etching to form the ridge 9 .
- a mask for selective growth is formed on the window regions to selectively grow a left upper cladding layer 4 f on both sides of the ridge in the gain region 10 ( FIGS. 12A and 12B ).
- a thickness of the left upper cladding layer 4 b in the gain region 10 can be formed to be thicker by a thickness of the left upper cladding layer 4 f selectively grown.
- the seventh embodiment related to the present invention is a process in which the left upper cladding layer 4 a in the window regions 11 is formed to be thinner than the left upper cladding layer 4 b in the gain region 10 , which is different from the process described in the first, fifth or seventh embodiment.
- the fabrication process is, to be concrete, a process fabricating a semiconductor laser element in which two grooves 30 parallel to each other are formed and a narrow region between the two grooves 30 serves as a ridge, wherein width values of a groove 30 in the regions A serving as the window regions is different from a width value of the groove 30 in the region B serving as the gain region, whereby the left upper cladding layer 4 a in the window regions 11 is formed to be thinner than the left upper cladding layer 4 b in the gain region 10 ( FIG. 13 and FIGS. 14A and 14B ).
- portions on both sides of the ridge are etched so that a width of each of the grooves 31 of a region A for forming a window is narrower than a width of each of the grooves 32 forming the gain region.
- an etching resist film is formed on the contact layer, and formed at both sides of a ridge are openings having widths thereof wider in first regions corresponding to edges of a semiconductor laser element and narrower in the other region thereof.
- the contact layer and the upper cladding layer are etched through openings of a mask to remove a stock down to a predetermined depth.
- etching progresses faster in the portion of a groove 31 .
- the left upper cladding layer 4 a in a window region 11 can be easily thinner than the left upper cladding layer 4 b in the gain region.
- an equivalent refractive index difference between the ridge and portions on both sides thereof in the window regions is made larger than an equivalent refractive index difference between the ridge and portions on both sides thereof in the gain region, a low aspect can be acquired without lowering a kink level.
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Abstract
A method of producing a semiconductor laser element including a step of growing a lower cladding layer, an active layer, a left upper cladding layer, a etching stopper layer having a multiple quantum well structure, an upper cladding layer and a contact layer in the order on a semiconductor substrate to form a laminate structure, a step of doping an impurity end portions near to edge surfaces of the laminate structure so as to cross over the active layer to form window regions and to make the etching stopper layer of window regions into disorder, a step of etching the contact layer in the window regions, a step of forming a protective film to form a ridge, and a step of etching both sides of the protective film with the protective film so as to cross over the disordered etching stopper layer.
Description
- This application is a divisional of application Ser. No. 11/515,747, filed Sep. 6, 2006, which is a divisional of U.S. application Ser. No. 10/842,461, filed May 11, 2004, and claims the benefit of priority from Japanese Patent Application No. 2003-182401, filed Jun. 26, 2003. The entire contents of which are incorporated herein by reference.
- 1. Field of the Invention
- The present invention relates to a semiconductor laser element, and particularly, to a semiconductor laser element used as a light source for an information recording apparatus.
- 2. Description of the Related Art
- A recording density in an optical disk for information recording has been increasingly raised because of development in digital information technology, and a high power capability has been simultaneously required in a semiconductor laser element, which is a light source for an information recording apparatus, because of improvement on an information recording speed onto an optical disk. It is unpreferable, however, to cause nonlinearity between a current and an optical output, such as a kink, in usage of the semiconductor laser element, and it is required to provide a semiconductor laser element that has no kink in high power state, in other words with a high kink level.
- In order to improve a recording speed, a semiconductor laser element is effective that has a lens system guiding light from a semiconductor laser element to an optical disk and a low aspect characteristic (a ratio of a vertical spread angle FFPy to a horizontal spread angle FFPx, FFPy/FFPx is small), with which a high optical coupling efficiency can be obtained.
- In such a way, it is necessary to use a semiconductor laser element with a high kink level and a low aspect ratio in order to improve a recording density.
- Japanese Non-examined Patent Publication No. 2-178988 is referred herein.
- There have been available the two methods to obtain a low aspect ratio: one method in which a small FFPy is adopted and the other in which a large FFPx is adopted, whereas problems have been arisen in both methods such that a temperature characteristic is degraded with a smaller FFPy adopted, while with a larger FFPx adopted, a kink level is lowered.
- Therefore, there has been conventionally difficulty in fabricating a high output laser with a low aspect.
- For example, if an FFPx is made larger in order to obtain a low aspect, light in a horizontal plane is required to be confined at a higher degree, wherein with confinement of light at a higher degree, inhomogeneity in carrier injection arises due to spatial hole burning, leading to generation of a kink.
- It is accordingly an object of the present invention to provide a semiconductor laser element having a structure capable of suppressing generation of a kink even in a case where an FFPx is made large.
- A semiconductor laser element related to the present invention has a ridge structure in which an active layer is provided between a semiconductor layer of one conductivity type and a semiconductor layer of the other conductivity type having a ridge, and window regions that are non-gain regions are provided at both ends thereof, wherein a difference in equivalent refractive index between the ridge and portions on both sides thereof in each of the window regions is larger than a difference in equivalent refractive index between the ridge and portions on both sides thereof in a gain region.
- The semiconductor laser element related to the present invention with such a construction can realize a low aspect ratio without lowering a kink level.
-
FIG. 1 is a sectional view of a semiconductor laser diode of a first embodiment related to the present invention in parallel to a resonance direction thereof. -
FIG. 2A is a sectional view taken on line A-A′ ofFIG. 1 in a window region of the semiconductor laser diode of a first embodiment andFIG. 2B is a sectional view taken on line B-B′ ofFIG. 1 in a gain region of the semiconductor laser diode thereof. -
FIG. 3 is a perspective view of a semiconductor laser element in process of the first embodiment after semiconductor layers are grown in a fabrication process therefor. -
FIG. 4 is a perspective view of a semiconductor laser element in process of the first embodiment after a contact layer is etched in the fabrication process therefor. -
FIG. 5 is a perspective view of a semiconductor laser element in process of the first embodiment after the first etching for forming a ridge ends in the fabrication process therefor. -
FIG. 6 is a perspective view of a semiconductor laser element in process of the first embodiment after the second etching for forming a ridge ends in the fabrication process therefor. -
FIG. 7A is a sectional view in a window region of a semiconductor laser diode related to an example modification of the first embodiment andFIG. 7B is a sectional view in a gain region of the semiconductor laser diode related to the example modification thereof. -
FIG. 8 is a perspective view of a semiconductor laser diode of a second embodiment. -
FIG. 9A is a sectional view in a window region of a semiconductor laser diode of a third embodiment andFIG. 9B is a sectional view in a gain region of the semiconductor laser diode thereof. -
FIG. 10 is a sectional view in a window region of a semiconductor laser diode related to an example modification of the third embodiment. -
FIG. 11 is a sectional view in a window region of a semiconductor laser diode of a fourth embodiment. -
FIG. 12A is a sectional view in a window region of a semiconductor laser diode of a sixth embodiment andFIG. 12B is a sectional view in a gain region of the semiconductor laser diode thereof. -
FIG. 13 is a sectional view of a semiconductor laser diode of a seventh embodiment related to the present invention in parallel to a resonance direction thereof. -
FIG. 14A is a sectional view in a window region of the semiconductor laser diode of a seventh embodiment andFIG. 14B is a sectional view in a gain region of the semiconductor laser diode thereof. - Description will be given of embodiments related to the present invention below with reference to the accompanying drawings.
- A semiconductor laser diode of the first embodiment related to the present invention is a ridge type semiconductor laser diode as shown in
FIGS. 2A and 2B and has a structure in which aridge 9 is formed so that part of upper cladding layer are left behind on anactive layer 3 on both sides of theridge 9, andwidow regions 11, which are non-gain regions for preventing an optical damage, are formed at both ends (FIG. 1 ). - In the semiconductor laser diode of the first embodiment, the left
upper cladding layer 4 a of thewindow regions 11 are formed so as to be thinner than the leftupper cladding layer 4 b of again region 10. - In the semiconductor laser diode of the first embodiment with such a construction, since an equivalent refractive index difference Δn11 in the non-gain regions, each of which is a window region, can be larger than an equivalent refractive index difference Δn10 in the gain region, an FFPx can be made large, thereby enabling a low aspect to be obtained.
- On the other hand, a
window region 11 in which the leftupper cladding layer 4 a is thin in thickness in order to increase the equivalent refractive index difference Δn11 is a non-gain region having no gain or a small gain; therefore, no chance to lower a kink level is encountered even with a light confinement at a great degree. - Therefore, the semiconductor laser element of the first embodiment can realize a low aspect without lowering a kink level.
- Then, description will be given of a fabrication process for a semiconductor laser element of the first embodiment related to the present invention with reference to
FIG. 3 . - In the fabrication process, epitaxially grown on a
semiconductor substrate 1 are alower cladding layer 2, a multiple quantum wellactive layer 3, a first leftupper cladding layer 41, an etching stopper layer ESL1, a second leftupper cladding layer 42, an etching stopper layer ESL2, anupper cladding layer 43 and acontact layer 6 in the order (FIG. 3 ). - Example materials of the substrate and the semiconductor layers are given in Table 1 in a case where a 660 nm semiconductor laser diode for DVD is constructed.
TABLE 1 Semiconductor substrate 1 n type GaAs substrate Lower cladding layer 2 n type (Al0.7Ga0.3)0.5In0.49P Multiple quantum well active active layer constituted of an undoped layer 3 Ga0.44In0.56P well layer and an undoped (Al0.5Ga0.5)0.51In0.49P barrier layer Upper cladding layer p type (Al0.7Ga0.3)0.51In0.49P layer Contact layer 6 p type GaAs layer - In Table 1, the upper cladding layer indicates the first left
upper cladding layer 41, the second leftupper cladding layer 42 and theupper cladding layer 43. - For example, p type Al0.3Ga0.7As layer can be used as the etching stopper layers ESL1 and ESL2.
- As another example, example materials for constituting a 780 nm semiconductor laser diode for CD are presented in Table 2.
TABLE 2 semiconductor substrate 1 n type GaAs substrate lower cladding layer 2 n type Al0.48Ga0.52As multiple quantum well active active layer constituted of an undoped layer 3 Al0.11Ga0.89As well layer and an undoped Al0.34Ga0.66As barrier layer upper cladding layer p type Al0.48Ga0.52As layer contact layer 6 p type GaAs layer - In Table 2, the upper cladding layer indicates the first left
upper cladding layer 41, the second leftupper cladding layer 42 and theupper cladding layer 43. - In the constructions using the GaAs substrate shown in Tables 1 and 2, Si, proton or Zn can be used as an impurity to form the
window regions 11. - The polarities of p and n types shown in Tables 1 and 2 may be reversed.
- Concrete materials are exemplified in the constructions shown in Tables 1 and 2, to which the present invention is not limited.
- After the epitaxial growth, an impurity is doped into portions of the regions A serving as the window regions so as to cross over the active layer by means of ion implantation, diffusion or the like. With such doping applied, the band gap of the doped active layer increases to form the
window regions 11 with no absorption of light. Thewindow regions 11 are non-gain regions with neither light absorption nor light amplification. - Note that the
window regions 11 are each formed in a end portion of a width of from 5 μm to 50 μm and, more preferably, from 20 μm to 30 μm inward from an edge surface. - Then, the
contact layer 6 is entirely or partially etched in the regions A serving as the window regions 11 (FIG. 4 ). - Thereafter, a protective film R1 for providing a ridge is formed and both sides of the protective film R1 are dry etched (
FIG. 5 ). In this step, etching conditions are set so that in the regions A, the secondleft cladding layer 42 is etched partway therein, while in the region B for forming the gain region, theupper cladding layer 43 is etched partway therein. - That is, in this fabrication process, a surface level difference in height between the regions A and the region B formed on both sides of the ridge is equal to a surface level difference in height between the regions A and the region B formed by etching the
contact layer 6, which is described usingFIG. 4 . - Then, all or some of the second left
upper cladding layer 42 and all or some of the rest of theupper cladding layer 43, which are exposed, are removed by wet etching. In this wet etching, the regions A are etched off as far as the first etching stopper layer ESL1, while the region B is etched off as far as the second etching stopper layer ESL2 (FIG. 6 ). - In such a fabrication process, by properly setting thickness values of the first left
upper cladding layer 41, the second leftupper cladding layer 42 and theupper cladding layer 43, desired thickness values of the leftupper cladding layer 4 a in thewindow regions 11 and the leftupper cladding layer 4 b in thegain region 10 can be easily formed with good reproducibility. - While in the semiconductor laser element of the first embodiment, description is given of a structure in which portions on both sides of the
ridge 9 are neither covered with a semiconductor material nor, in other words, buried in a semiconductor material, the present invention is not limited to this construction, but can also be applied to a laser element having a structure in which theridge 9 are, as shown inFIGS. 7A and 7B , buried in acurrent blocking layer 21 on both sides thereof. Note thatFIG. 7A is a sectional view of a window region andFIG. 7B is a sectional view of the gain region. - A semiconductor laser element of the second embodiment related to the present invention is constructed in a similar manner to that in the first embodiment with the exceptions described below (
FIG. 8 ). - Note that in
FIG. 8 , like symbols are attached to constituents similar to those in the first embodiment. -
Distinction 1 - In the semiconductor laser diode of the second embodiment, a left
upper cladding layer 4 c with the same thickness is formed across again region 10 includingwindow regions 11 on active layer on both sides of a ridge. -
Distinction 2 - A current blocking layer (buried layer) 21 is formed only on both sides of the ridge in the
gain region 10. - In the semiconductor laser diode of the second embodiment with such a construction as well, an equivalent refractive index difference Δn11 between the ridge and portions on both sides thereof in non-gain regions (window regions) can be larger than an equivalent refractive index difference Δn10 between the ridge and portions on both sides thereof in the
gain region 10. - Therefore, in the construction of the second embodiment as well, an FFPx can be large to thereby obtain a low aspect and since the window regions larger in equivalent refractive index difference Δn11 are non-gain regions, no reduction in kink level occurs even in light confinement at a higher degree.
- Accordingly, an action and effect similar to those in the first embodiment can be obtained using a semiconductor laser element of the second embodiment.
- A semiconductor laser element of the third embodiment related to the present invention is constructed in a similar manner to that in the second embodiment except that formed on both sides of a ridge in
window regions 11 is a buriedlayer 21 a made of a semiconductor material having a refractive index smaller than thecurrent blocking layer 21 formed on both sides of the ridge in a gain region 10 (FIGS. 9A and 9B ). - Note that in
FIGS. 9A and 9B , like symbols are attached to constituents similar to those in the first or second embodiment. - In the semiconductor laser diode of the third embodiment with such a construction, an equivalent refractive index difference Δn11 between the ridge and portions on both sides thereof in non-gain regions (window regions) can be larger than an equivalent refractive index difference Δn10 between the ridge and portions on both sides thereof in the
gain region 10. - Therefore, in the construction of the third embodiment as well, an FFPx can be large to thereby obtain a low aspect and since the window regions larger in equivalent refractive index difference Δn11 are non-gain regions, no reduction in kink level occurs even in light confinement at a higher degree.
- Accordingly, an action and effect similar to those in the first or second embodiment can be obtained using a semiconductor laser element of the third embodiment.
- While in the third embodiment described above, the buried
layer 21 a made of a semiconductor material having a refractive index smaller than thecurrent blocking layer 21 is formed on both sides of the ridge in thewindow regions 11, another construction may be adopted in which a buried layer made of a similar semiconductor material is formed on both sides of the ridge in thewindow region 11 and on both sides of the ridge in thegain region 10 with the exception that a carrier concentration in the buried layer on both sides of the ridge in thewindow regions 11 is higher than that in the buried layer on both sides of the ridge in thegain region 10, so that the buried layer in thewindow regions 11 is a high carrier concentration buriedlayer 21 b (FIG. 10 ). - With such a construction adopted, a refractive index of the high carrier concentration buried
layer 21 b can be rendered small due to a plasma effect, thereby enabling an action and effect similar to those in the third embodiment to be obtained. - A semiconductor laser element of the fourth embodiment related to the present invention is constructed such that
current blocking layer 21 c is formed using a material absorbing laser oscillated light, for example GaAs on both sides of a ridge inwindow regions 11. - Note that a construction of a
gain region 10 may be similar to that in the first embodiment or in the second embodiment (inFIG. 11 , the construction is depicted as being similar to that in the second embodiment). - In the semiconductor laser element of the fourth embodiment with such a construction, light is absorbed by the
current blocking layer 21 c, thereby enabling a spot size in a horizontal plane at an end surface thereof to be reduced. - With a smaller spot size in a horizontal plane, a far field pattern (FFPx) in a horizontal plane can be enlarged due to a diffraction phenomenon of light, thereby enabling a low aspect to be realized without lowering a kink level.
- The fifth embodiment related to the present invention is a process in which the left
upper cladding layer 4 a in thewindow regions 11 is formed to be thinner than the leftupper cladding layer 4 b in thegain region 10, which is different from the process described in the first embodiment. - To be concrete, this fabrication process is different from the process described in the first embodiment in that the etching stopper layer ESL2 is a multiple quantum well structure and no etching stopper layer ESL1 is formed. That is, in this process, the first left
upper cladding layer 41 and the second leftupper cladding layer 42 are formed continuously with the same material. - Herein, the etching stopper layer ESL2 of a multiple quantum well structure can be a multiple quantum well structure constructed of a Ga0.58In0.42P well layer and an (Al0.5Ga0.5)0.5In0.49P barrier layer.
- Then, an impurity is, in a similar manner to that in the first embodiment, doped in the regions A used for forming window regions by means of ion implantation, diffusion or the like. With the doping, the etching stopper layer ESL2 of a multiple quantum well structure in the window regions are degenerated into disorder and loses an etching stopper function.
- After such a processing, etching is conducted for forming the ridge, whereby in the window regions, etching progresses beyond the etching stopper layer ESL2, while in the gain region, etching is stopped by the etching stopper layer ESL2.
- After the step, a thickness of the left
upper cladding layer 4 a in thewindow regions 11 can be thinner than that of the leftupper cladding layer 4 b in thegain region 10 with ease. - The sixth embodiment related to the present invention is a fabrication process fabricating an element having a structure shown in the first embodiment without forming an etching stopper layer.
- To be concrete, in the sixth embodiment, a left
upper cladding layer 4 e with the same thickness is formed across thegain region 10 including thewindow regions 11 on both sides of theridge 9 in etching to form theridge 9. A mask for selective growth is formed on the window regions to selectively grow a leftupper cladding layer 4 f on both sides of the ridge in the gain region 10 (FIGS. 12A and 12B ). - In such a way, a thickness of the left
upper cladding layer 4 b in thegain region 10 can be formed to be thicker by a thickness of the leftupper cladding layer 4 f selectively grown. - According to a fabrication process of the sixth embodiment, a semiconductor laser element having a structure of the first embodiment with ease.
- The seventh embodiment related to the present invention is a process in which the left
upper cladding layer 4 a in thewindow regions 11 is formed to be thinner than the leftupper cladding layer 4 b in thegain region 10, which is different from the process described in the first, fifth or seventh embodiment. - The fabrication process is, to be concrete, a process fabricating a semiconductor laser element in which two
grooves 30 parallel to each other are formed and a narrow region between the twogrooves 30 serves as a ridge, wherein width values of agroove 30 in the regions A serving as the window regions is different from a width value of thegroove 30 in the region B serving as the gain region, whereby the leftupper cladding layer 4 a in thewindow regions 11 is formed to be thinner than the leftupper cladding layer 4 b in the gain region 10 (FIG. 13 andFIGS. 14A and 14B ). - That is, in the process, portions on both sides of the ridge are etched so that a width of each of the
grooves 31 of a region A for forming a window is narrower than a width of each of thegrooves 32 forming the gain region. - To be more concrete, an etching resist film is formed on the contact layer, and formed at both sides of a ridge are openings having widths thereof wider in first regions corresponding to edges of a semiconductor laser element and narrower in the other region thereof.
- Then, the contact layer and the upper cladding layer are etched through openings of a mask to remove a stock down to a predetermined depth.
- In the etching through the mask, since in a portion of a
groove 31 narrower in width (etching region), a supply speed for an etching agent is faster than in a portion of the groove wider in width, etching progresses faster in the portion of agroove 31. Thereby, the leftupper cladding layer 4 a in awindow region 11 can be easily thinner than the leftupper cladding layer 4 b in the gain region. - As described above, in a fabrication process of the seventh embodiment as well, it is possible to fabricate a low aspect semiconductor laser diode with a high kink level.
- As detailed above, in a semiconductor laser element related to the present invention, since an equivalent refractive index difference between the ridge and portions on both sides thereof in the window regions is made larger than an equivalent refractive index difference between the ridge and portions on both sides thereof in the gain region, a low aspect can be acquired without lowering a kink level.
Claims (2)
1. A method of producing a semiconductor laser element comprising:
a step of growing a lower cladding layer, an active layer, a left upper cladding layer, a etching stopper layer having a multiple quantum well structure, an upper cladding layer and a contact layer in the order on a semiconductor substrate to form a laminate structure;
a step of doping an impurity end portions near to edge surfaces of the laminate structure so as to cross over the active layer to form window regions and to make the etching stopper layer of window regions into disorder;
a step of etching the contact layer in the window regions;
a step of forming a protective film to form a ridge;
a step of etching both sides of the protective film with the protective film so as to cross over the disordered etching stopper layer.
2. A method of producing a semiconductor laser element comprising:
a step of growing a lower cladding layer, an active layer, a first left upper cladding layer, an upper cladding layer and a contact layer in the order on a semiconductor substrate to form a laminate structure;
a step of doping an impurity end portions near to edge surfaces of the laminate structure so as to cross over the active layer to form window regions;
a step of forming a protective film to form a ridge;
a step of etching both sides of the protective film with the protective film up to the first left upper cladding layer;
a step of forming a selectively growth mask on the window regions;
a step of selectively growing a second left upper cladding layer on the first left upper cladding layer.
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JP2003182401A JP4472278B2 (en) | 2003-06-26 | 2003-06-26 | Semiconductor laser element |
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DE102016113071A1 (en) * | 2016-07-15 | 2018-01-18 | Osram Opto Semiconductors Gmbh | Semiconductor laser diode |
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Also Published As
Publication number | Publication date |
---|---|
JP4472278B2 (en) | 2010-06-02 |
KR100653322B1 (en) | 2006-12-04 |
KR20050001366A (en) | 2005-01-06 |
CN1578028A (en) | 2005-02-09 |
US7561608B2 (en) | 2009-07-14 |
CN100346544C (en) | 2007-10-31 |
CN100514777C (en) | 2009-07-15 |
US20040264520A1 (en) | 2004-12-30 |
DE102004029423A1 (en) | 2005-02-17 |
JP2005019679A (en) | 2005-01-20 |
TW200501526A (en) | 2005-01-01 |
TWI244248B (en) | 2005-11-21 |
CN101043123A (en) | 2007-09-26 |
US20070004072A1 (en) | 2007-01-04 |
US20070002916A1 (en) | 2007-01-04 |
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