JP2005229016A - Semiconductor laser element, manufacturing method thereof, optical transmitting system, and optical disk apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the variation of the optical-confinement characteristic of a semiconductor laser element and the degradation of its resistance which are caused by the turbulence of its crystal quality generated in the case of its crystal re-growth, and eliminate the variation of its horizontal optical confinement characteristic which is caused by the spontaneous superlatticing of its InGaP layer. <P>SOLUTION: In the semiconductor laser element, an InGaAsP etching stopping layer 29 and an AlGaAs current blocking layer 30 are formed successively on a first GaAs semiconductor layer 28 formed above an active layer 25. Therefore, the etching rate of the semiconductor laser element becomes slow according as its P mixed-crystal ratio in V-group element has got smaller compared with the conventional case to form an In Ga P layer. Consequently, the side etching of the AlGaAs current blocking layer 30 is so suppressed when forming a stripe-form groove 33 by removing the etching stopping layer 29 as to prevent the turbulence of its crystal quality generated in its re-growth process, and as to be able to prevent resultantly the variation of its optical-confinement characteristic and the degradation of its resistance. Further, since no spontaneous superlatticing problem exists in its InGaAsP material, the variation of its optical confinement characteristic which is caused by its refractive-index variation generated by spontaneous superlatticing can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser element, and in particular, a semiconductor laser element used in an optical transmission system, an optical disc apparatus, etc., a manufacturing method thereof, an optical transmission system using the semiconductor laser element, and the semiconductor laser element The present invention relates to an optical disc apparatus.

  10 to 12 are cross-sectional views in each manufacturing process of a conventional semiconductor laser device (see, for example, Japanese Patent Laid-Open No. 2001-267689 (Patent Document 1)). A conventional semiconductor laser device and a method for manufacturing the same will be described below with reference to FIGS.

First, as shown in FIG. 10, an n-Al _X1 Ga _{1 -X1} As lower cladding layer 2 (0.1 ≦ x1 ≦ 0) is formed on an n-GaAs substrate 1 by MOCVD (metal organic chemical vapor deposition). .5), n or _{i-In X2 Ga 1-X2} As 1-y2 P y2 optical waveguide layer 3 (x2 = 0.49 ± 0.01,0 ≦ y2 ≦ 0.3), the compressive strain an In _X3 Ga _{1 -X3} As _1-y3 P _y3 quantum well active layer 4 (0 <x3 ≦ 0.4, 0 ≦ y3 ≦ 0.1), p or i-In _X2 Ga _1-X2 As _1-y2 P _y2 optical waveguide layer 5, p-GaAs first etching blocking layer 6, n-InGaP second etching blocking layer 7, n-Al _X4 Ga _1-X4 As current confinement layer 8 (0.1 ≦ x4 ≦ 0.8, x1 <x4) And the n-GaAs cap layer 9 are sequentially formed. Further, an SiO ₂ film 10 is formed thereon, and the stripe region SiO ₂ film 10 having a width of about 3 μm in the (011) direction is removed by ordinary photolithography.

Next, as shown in FIG. 11, by using the SiO ₂ film 10 as a mask, the n-GaAs cap layer 9 and the n-Al _X4 Ga _1-X4 As current confinement layer 8 are etched with a sulfuric acid-based etchant. The n-InGaP second etching stop layer 7 is exposed.

Next, as shown in FIG. 12, the SiO ₂ film 10 is removed with a hydrofluoric acid-based etchant. Subsequently, using the n-GaAs cap layer 9 as a mask, the n-InGaP second etching stop layer 7 on the groove bottom is etched with a hydrochloric acid-based etchant to expose the p-GaAs first etching stop layer 6. Thereafter, a p-Al _X1 Ga _{1 -X1} As upper clad layer 11 and a p-GaAs contact layer 12 are formed on the entire surface. Then, after forming the p-side electrode 13 on the p-GaAs contact layer 12, the n-GaAs substrate 1 is polished, and the n-side electrode 14 is formed on the polished back side of the n-GaAs substrate 1.

  A high reflectivity coat and a low reflectivity coat are applied to the resonator surface formed by cleaving the semiconductor multilayer structure formed as described above, and then a chip is formed to form a semiconductor laser device. .

  According to the semiconductor laser device, at the interface where the p-AlGaAs upper clad layer 11 is regrown, the layer containing Al that is easily oxidized is only the n-AlGaAs current confinement layer 8, and the exposed portion is Only the side surface of the etching groove. Therefore, the AlGaAs upper cladding layer 11 can be easily regrown and the reliability can be improved.

  In addition, GaAs is used for the first etching blocking layer 6 and InGaP is used for the second etching blocking layer 7 as an etching blocking layer for forming a groove having an internal stripe structure. By doing so, the GaAs first etching blocking layer 6 is not etched by the hydrochloric acid-based etchant. Therefore, the GaAs first etching blocking layer 6 is automatically etched by etching the InGaP second etching blocking layer 7 with the hydrochloric acid-based etchant. Etching can be stopped at the upper surface of the substrate. Therefore, the controllability of the stripe width by wet etching can be improved.

  However, the conventional semiconductor laser device has the following problems. That is, the InGaP material used for the second etch stop layer 7 has a very good etching selectivity with respect to the GaAs material and the AlGaAs material when a hydrochloric acid-based etchant is used, and the etching speed is high. Therefore, when the InGaP second etching blocking layer 7 is removed, side etching proceeds quickly to the n-AlGaAs current confinement layer 8, and an eave-like step is formed on the side surface of the stripe groove. Therefore, when the p-AlGaAs upper cladding layer 11 is subsequently formed by crystal regrowth, disorder of crystallinity occurs from the eaves-shaped step portion, and the desired optical confinement effect cannot be obtained, or the element resistance There is a problem of causing deterioration.

  Furthermore, an interface layer containing an extremely thin P in which both materials are mixed with each other may be formed at the interface between GaAs and InGaP. In the above-described removal step of the InGaP layer using a hydrochloric acid-based etchant, the P There is a case where the interface layer containing can not be removed. In that case, even when the upper cladding layer 11 is regrown on the interface layer containing P that remains without being removed, the crystallinity of AlGaAs forming the upper cladding layer 11 may be lowered.

  The InGaP layer is likely to change to a natural superlattice structure depending on crystal growth conditions. And when changing to the natural superlattice structure, the refractive index may fluctuate. The presence of such a material whose refractive index tends to fluctuate between the active layer 4 and the upper clad layer 11, in particular, the optical confinement characteristic in the horizontal direction with respect to the active layer 4 is due to the variation in the refractive index during manufacturing. There is a problem that it fluctuates.

  Further, when AlGaAs is crystal-grown as the upper clad layer 11, the crystal is usually grown at as high a temperature as possible in order to prevent oxygen from being taken in during the growth. However, at this time, since the p-type dopant re-evaporates from the GaAs first etching stop layer 6 serving as the regrowth interface, the resistance value at the regrowth interface increases or the regrowth increases as the doping concentration decreases. There is also a problem that the roughness of the interface deteriorates.

Japanese Patent Laid-Open No. 2001-267689 (page 6, FIG. 1)

  Therefore, the problem of the present invention is that the optical confinement characteristics change due to the disorder of crystallinity during crystal regrowth, the device resistance deteriorates, the crystallinity of the upper cladding layer decreases due to the influence of the P-based interface layer remaining at the regrowth interface, Overcoming problems such as fluctuations in optical confinement characteristics in the horizontal direction due to natural superlattice formation of InGaP layer and deterioration of interface resistance and interface flatness due to dopant re-evaporation from the regrown interface, reproducibility of desired optical confinement characteristics A semiconductor laser element that can be well realized, has a good element resistance, and has high reliability, a method for manufacturing the semiconductor laser element, an optical transmission system using the semiconductor laser element, and the semiconductor laser element It is to provide an optical disc apparatus.

  In order to solve the above-described problems, the present invention provides at least a first conductivity type lower cladding layer, an active layer, a second conductivity type upper first cladding layer, and a first GaAs semiconductor layer on a first conductivity type GaAs substrate. , In the semiconductor laser element stacked in order, a current injection region and a current non-injection region are provided on the first GaAs semiconductor layer, and at least the InGaAsAsP semiconductor layer and the first conductivity type AlGaAs are provided in the current non-injection region. A semiconductor layer is formed, and a second conductivity type AlGaAs upper second cladding layer is formed on the InGaAsP semiconductor layer or AlGaAs semiconductor layer in the current non-injection region and in the current injection region. It is characterized by that.

  According to the above configuration, the InGaAsAs semiconductor layer is formed in the current non-injection region on the first GaAs semiconductor layer. Therefore, the etching rate can be slowed by the amount of the P mixed crystal ratio in the group V element as compared with the case where the InGaP layer is formed as in the conventional semiconductor laser device shown in FIGS. As a result, side etching with respect to the AlGaAs semiconductor layer formed on the InGaAsAs semiconductor layer is suppressed when the current injection region is formed by partially etching away the InGaAsAs semiconductor layer. Therefore, when the AlGaAs upper second cladding layer is regrown in the current injection region, the crystallinity is not disturbed. Therefore, the device resistance is not deteriorated and a desired optical confinement characteristic can be obtained. Further, the InGaAsP material does not form the natural superlattice. Therefore, there is no change in the optical confinement characteristic in the horizontal direction due to the change in the refractive index due to the natural superlattice.

  In the present specification, the “first conductivity type” and the “second conductivity type” refer to n-type or p-type, and when the “first conductivity type” is n-type, “second conductivity type”. Is p-type, and when the “first conductivity type” is p-type, the “second conductivity type” is n-type.

  In one embodiment, the second GaAs semiconductor is formed above the InGaAsAs semiconductor layer or AlGaAs semiconductor layer in the current non-injection region and below the AlGaAs upper second cladding layer in the current injection region. A layer is formed, and the first GaAs semiconductor layer and the second GaAs semiconductor layer are in close contact with each other in the current injection region.

  According to this embodiment, in addition to the configuration of the semiconductor laser element, a second GaAs semiconductor layer is formed immediately below the AlGaAs upper second cladding layer, and the first GaAs semiconductor layer and the second GaAs semiconductor layer are formed in the current injection region. The 2 GaAs semiconductor layer is in close contact. Thus, by forming a regrowth interface with the same kind of material of the first GaAs semiconductor layer and the second GaAs semiconductor layer in the current injection region, it is possible to achieve an effect that the interface resistance is hardly deteriorated.

  In the semiconductor laser device having the second GaAs semiconductor layer of one embodiment, the first GaAs semiconductor layer and the second GaAs semiconductor layer are of the second conductivity type.

  According to this embodiment, the interface resistance can be further reduced by making the conductivity type of the semiconductor layer made of the same material constituting the regrowth interface of the current injection region the same.

  In the semiconductor laser device having the second GaAs semiconductor layer of one embodiment, the first GaAs semiconductor layer is of a second conductivity type having a doping concentration lower than that of the second GaAs semiconductor layer.

  In this embodiment, the first GaAs semiconductor layer having a second conductivity type doping concentration lower than the doping concentration of the second GaAs semiconductor layer is obtained by re-growing the second conductivity type second GaAs semiconductor layer on the intrinsic first GaAs semiconductor layer. By doing so, a dopant of the second conductivity type is formed by diffusing from the second GaAs semiconductor layer regrown in close contact with the first GaAs semiconductor layer. In that case, the intrinsic first GaAs semiconductor layer functions as a diffusion preventing layer of the second conductivity type dopant from the second GaAs semiconductor layer to the active layer. Therefore, it is possible to prevent the dopant from diffusing and moving to the active layer, and it is possible to prevent a decrease in reliability and fluctuations in electrical characteristics and optical characteristics.

  In the semiconductor laser device having the second GaAs semiconductor layer of the second conductivity type according to one embodiment, the second GaAs semiconductor layer is of the second conductivity type using Zn as a dopant.

  According to this embodiment, by using zinc (Zn) as the second conductivity type dopant, the intrinsic first GaAs semiconductor layer in the current injection region can be easily converted to the second conductivity type by diffusion. Moreover, since the intrinsic first GaAs semiconductor layer functions well as a diffusion preventing layer for Zn dopant from the second GaAs semiconductor layer to the active layer, the Zn dopant is prevented from diffusing and moving to the active layer. Therefore, it is possible to prevent a decrease in reliability and fluctuations in electrical characteristics and optical characteristics.

  Further, in the semiconductor laser device having the second conductivity type second GaAs semiconductor layer of one embodiment, the thickness of the first GaAs semiconductor layer in the current injection region is not less than 40 mm and not more than 200 mm.

  According to this embodiment, since the thickness of the first GaAs semiconductor layer in the current injection region is 40 mm or more, the effect as a diffusion preventing layer for dopant from the second GaAs semiconductor layer can be remarkably exhibited. Further, since the thickness is 200 mm or less, a low-concentration GaAs layer having a high resistance does not remain in the current injection region of the semiconductor laser element, and deterioration of the element resistance can be suppressed.

  In the semiconductor laser device of one embodiment, the thickness in the current injection region in the first GaAs semiconductor layer is thinner than the thickness in the current non-injection region.

  According to this embodiment, when an InGaAsAs semiconductor layer and an AlGaAs semiconductor layer are grown on the first GaAs semiconductor layer, the current injection region is formed by partially removing the AlGaAs semiconductor layer and the InGaAsAsP semiconductor layer. The interface layer containing very thin P formed at the interface between the first GaAs semiconductor layer and the InGaAsAs semiconductor layer is removed in the current injection region. Therefore, in the current injection region, a crystal regrowth interface having no P-containing interface layer can be realized, and the interface resistance can be reduced and the device characteristics can be improved.

  In the semiconductor laser device of one embodiment, the InGaAsP semiconductor layer is intrinsic or of the second conductivity type.

  According to this embodiment, in the current non-injection region, the intrinsic or second conductivity type InGaAsAs semiconductor layer is the first conductivity type from the first conductivity type AlGaAs semiconductor layer formed on the InGaAsAsP semiconductor layer. It functions as a dopant diffusion preventing layer. Therefore, it is possible to prevent the dopant from diffusing and moving to the active layer side, and it is possible to prevent a decrease in reliability and a change in electrical characteristics and optical characteristics.

  In the semiconductor laser device of one embodiment, the mixed crystal ratio of P in the group V element in the InGaAsAs semiconductor layer is 0.4 or more and 0.6 or less.

  According to this embodiment, since the mixed crystal ratio of P in the group V element in the InGaAsAs semiconductor layer is 0.4 or more, the InGaAsAs semiconductor layer has sufficient etching selectivity with respect to the AlGaAs semiconductor layer. However, the interface layer containing very thin P formed at the interface between the first GaAs semiconductor layer and the InGaAsP semiconductor layer is effectively removed. Furthermore, since the mixed crystal ratio of P is 0.6 or less, the side etching with respect to the AlGaAs semiconductor layer is sufficiently suppressed and the etching selectivity with respect to the first GaAs semiconductor layer is sufficient. It is possible to prevent formation of a passive layer that is difficult to be etched at the interface and has high resistance.

  In the semiconductor laser device of one embodiment, the Al mixed crystal ratio in the group III element in the AlGaAs semiconductor layer is larger than the Al mixed crystal ratio in the group III element in the AlGaAs upper second cladding layer. .

  According to this embodiment, a real guide type semiconductor laser device with little optical loss can be realized. Therefore, the oscillation threshold can be reduced.

  The present invention also provides a semiconductor laser device in which at least a first conductivity type lower cladding layer, an active layer, and a second conductivity type upper first cladding layer are sequentially laminated on a first conductivity type GaAs substrate. In the manufacturing method, a step of crystal-growing a first GaAs semiconductor layer, an InGaAsAs semiconductor layer, and a first conductivity type AlGaAs semiconductor layer on the upper first cladding layer, and removing a part of the AlGaAs semiconductor layer to make a current injection region A step of removing the InGaAsP semiconductor layer in the current injection region to partially expose the first GaAs semiconductor layer, and a surface portion of the exposed portion of the first GaAs semiconductor layer having a predetermined depth. And a step of crystal re-growth of the second conductivity type upper second cladding layer in at least the current injection region.

  According to the above configuration, the InGaAsAs semiconductor layer and the AlGaAs semiconductor layer are formed on the first GaAs semiconductor layer. Therefore, the etching rate can be slowed by the amount of the P mixed crystal ratio in the group V element as compared with the case where the InGaP layer is formed as in the conventional semiconductor laser device shown in FIGS. As a result, side etching on the AlGaAs semiconductor layer is suppressed when the InGaAsAs semiconductor layer in the current injection region is removed by etching. Therefore, the disorder of crystallinity does not occur when the upper second cladding layer is regrown in the current injection region. Therefore, the device resistance is not deteriorated and a desired optical confinement characteristic can be obtained.

  Further, the InGaAsP material does not form the natural superlattice. Therefore, there is no change in the optical confinement characteristic in the horizontal direction due to the change in the refractive index due to the natural superlattice. Furthermore, an exposed surface portion of the exposed portion of the first GaAs semiconductor layer is removed to a predetermined depth, so that an interface layer containing very thin P formed at the interface between the first GaAs semiconductor layer and the InGaAsAs semiconductor layer is formed. It is removed in the current injection region. Therefore, in the current injection region, a crystal regrowth interface without the interface layer containing P can be realized, and the interface resistance can be reduced and the device characteristics can be improved.

  In the method of manufacturing a semiconductor laser device according to one embodiment, after the surface portion of the exposed portion in the first GaAs semiconductor layer is removed to a predetermined depth, before the upper second cladding layer is regrown. The method further includes the step of crystal regrowth of the second GaAs semiconductor layer at least in the current injection region.

  According to this embodiment, in the current injection region, the second GaAs semiconductor layer is formed immediately below the upper second cladding layer, and the first GaAs semiconductor layer and the second GaAs semiconductor layer are in close contact with each other. Thus, by forming a regrowth interface with the same kind of material of the first GaAs semiconductor layer and the second GaAs semiconductor layer in the current injection region, it is possible to achieve an effect that the interface resistance is hardly deteriorated.

  In the method of manufacturing a semiconductor laser device according to one embodiment, the first GaAs semiconductor layer is intrinsic while the second GaAs semiconductor layer is of a second conductivity type. When the second GaAs semiconductor layer is regrown, The first GaAs semiconductor layer is converted to the second conductivity type by the diffusion of the dopant from the second GaAs semiconductor layer.

  According to this embodiment, the intrinsic first GaAs semiconductor layer has the second conductivity type dopant from the second GaAs semiconductor layer when the second conductivity type second GaAs semiconductor layer is crystal regrown thereon. Functions as a diffusion prevention layer. Therefore, it is possible to prevent the dopant from diffusing and moving to the active layer, and it is possible to prevent a decrease in reliability and fluctuations in electrical characteristics and optical characteristics.

  In the method of manufacturing a semiconductor laser device according to one embodiment, the second GaAs semiconductor layer is regrown using MOCVD.

  According to this embodiment, by using the MOCVD (metal organic chemical vapor deposition) method excellent in mass productivity, the throughput in the process of re-growing the second GaAs semiconductor layer is improved, and the semiconductor laser device can be manufactured at a lower cost. Can be manufactured. The above growth can also be performed using an MBE (molecular beam epitaxy) method instead of the MOCVD method.

  In the manufacturing method of the semiconductor laser device using the MOCVD method for crystal regrowth of the second GaAs semiconductor layer of one embodiment, the growth temperature of the second GaAs semiconductor layer is 500 ° C. or more and 600 ° C. or less.

  According to this embodiment, since the growth temperature of the second GaAs semiconductor layer is 500 ° C. or higher, there is no possibility that the growth mechanism of the second GaAs semiconductor layer is changed and the crystallinity is lowered. Furthermore, since the growth temperature is 600 ° C. or lower, the re-evaporation of the semiconductor material and the dopant from each layer, which is the foundation of crystal regrowth exposed in the current injection region, is suppressed, and deterioration of device characteristics is prevented. The

  The optical transmission system of the present invention is characterized by using the semiconductor laser device of the present invention.

  According to the above configuration, the semiconductor laser has high reliability without deteriorating element resistance, obtaining desired optical confinement characteristics, and without causing fluctuations in optical confinement characteristics due to refractive index fluctuations due to natural superlattices. Since the element is used, the power consumption of the optical transmission system is kept lower than that of the conventional optical transmission system, and the life is extended. Therefore, when this optical transmission system is mounted on a portable device or the like, the operation time becomes longer than before.

  The optical disc apparatus of the present invention is characterized by using the semiconductor laser element of the present invention.

  According to the above configuration, the semiconductor laser has high reliability without deteriorating element resistance, obtaining desired optical confinement characteristics, and without causing fluctuations in optical confinement characteristics due to refractive index fluctuations due to natural superlattices. Since the element is used, the power consumption of the optical disk apparatus can be suppressed lower than that of the conventional optical disk apparatus.

  As apparent from the above, the semiconductor laser device according to the present invention has the conventional InGaAsP semiconductor layer formed in the current non-injection region on the first GaAs semiconductor layer formed on the upper first cladding layer. As described above, the etching rate can be reduced as compared with the case where the InGaP layer is formed. Therefore, side etching of the AlGaAs semiconductor layer when the current injection region is formed by etching can be suppressed, and disorder of crystallinity during regrowth in the current injection region can be prevented, thereby preventing deterioration of element resistance. Desired light confinement characteristics can be obtained. Further, the InGaAsP material does not form the natural superlattice. Therefore, it is possible to prevent fluctuations in optical confinement characteristics due to fluctuations in refractive index due to natural superlattices.

  In the method of manufacturing a semiconductor laser device according to the present invention, the first GaAs semiconductor layer, the InGaAsAs semiconductor layer, and the AlGaAs semiconductor layer are formed on the upper first cladding layer. Therefore, the InGaAs layer is formed as in the conventional semiconductor laser device. Compared to the case, the etching rate for the InGaAsP semiconductor layer can be reduced. Therefore, after etching away a part of the AlGaAs semiconductor layer, side etching with respect to the AlGaAs semiconductor layer when etching away a part of the InGaAsAs semiconductor layer is suppressed, and regrowth is performed in the current injection region. The disorder of crystallinity can be prevented. As a result, it is possible to prevent the device resistance from deteriorating due to the disorder of crystallinity and to obtain desired optical confinement characteristics. Further, the InGaAsP material does not form the natural superlattice. Therefore, it is possible to prevent fluctuations in optical confinement characteristics due to fluctuations in refractive index due to natural superlattices. Further, since the surface portion of the exposed portion of the first GaAs semiconductor layer is removed to a predetermined depth, the current injection region includes very thin P formed at the interface between the first GaAs semiconductor layer and the InGaAsAs semiconductor layer. The interface layer can be removed. Therefore, the interface resistance can be reduced and the device characteristics can be improved.

  In addition, the optical transmission system of the present invention does not deteriorate the element resistance, obtains a desired optical confinement characteristic, does not cause a change in optical confinement characteristic due to a change in refractive index due to natural superlattice, and has high reliability. Since the semiconductor laser device of the present invention having the above is used, the power consumption of the optical transmission system can be kept lower than that of the conventional optical transmission system, and the life can be extended. Therefore, when this optical transmission system is mounted on a portable device or the like, the operation time can be made longer than before.

  In addition, the optical disk apparatus of the present invention does not deteriorate the element resistance, obtains a desired optical confinement characteristic, does not cause a change in the optical confinement characteristic due to a change in the refractive index due to the natural superlattice, and has high reliability. Since the semiconductor laser element according to the present invention is used, the power consumption of the optical disk apparatus can be kept lower than that of the conventional optical disk apparatus.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

First Embodiment FIG. 1 is a cross-sectional view showing a schematic structure of a semiconductor laser device according to the present embodiment. In the present embodiment, the first conductivity type is n-type, and the second conductivity type is p-type.

In this semiconductor laser device, on an n-type GaAs substrate 21, an n-type GaAs buffer layer 22, an n-type Al _0.6 Ga _0.4 As lower cladding layer 23, an n-type Al _0.4 Ga _0.6 As first light guide layer 24, multiple strain quanta. Well active layer 25, p-type Al _0.4 Ga _0.6 As second light guide layer 26, p-type Al _0.5 Ga _0.5 As upper first cladding layer 27, partially p-type i-type first GaAs semiconductor layer 28, i-type An In _0.245 Ga _0.755 As _0.54 P _0.46 etch stop layer 29, an n-type Al _0.6 Ga _0.4 As current blocking layer 30, and an n-type GaAs protective layer 31 are sequentially stacked. The n-type GaAs protective layer 31, the n-type AlGaAs current blocking layer 30, and the i-type InGaAsP etch stop layer 29 are provided with stripe-shaped grooves 33 serving as current channels (current injection regions) for current confinement. Yes. The first GaAs semiconductor layer 28 is p-type only in the current injection region and i-type in the remaining region. A p ⁺ -type second GaAs semiconductor layer 34 is formed on the n-type GaAs protective layer 31 and in the groove 33, and the p-type Al _0.5 Ga _0.5 As upper second cladding is formed on the p ⁺ -type second GaAs semiconductor layer 34. A layer 35, a p-type GaAs contact layer 36, and a p ⁺ -type GaAs contact layer 37 are sequentially formed.

On the back side of the n-type GaAs substrate 21, an n-side electrode 38 made of a multilayer metal thin film in which AuGe / Ni / Au is sequentially laminated is formed. On the p ⁺ -type GaAs contact layer 37, a p-side electrode 39 made of a multilayer metal thin film in which Ti / Pt / Au is sequentially stacked is formed.

  2 to 4 are cross-sectional views in each manufacturing process of the semiconductor laser device having the configuration shown in FIG. The method for manufacturing the semiconductor laser device will be described in detail below with reference to FIGS.

First, as shown in FIG. 2, an n-type GaAs buffer layer 22 (thickness: 0.5 μm, Si doping: 7.2 × 10 ¹⁷ cm ⁻³ ) is formed on an n-type GaAs substrate 21 having a (100) plane. N-type Al _0.6 Ga _0.4 As lower cladding layer 23 (thickness: 1.6 μm, Si-doped: 5.4 × 10 ¹⁷ cm ⁻³ ), n-type Al _0.4 Ga _0.6 As first light guide layer 24 (thickness) : 0.1 μm, Si doping: 5.4 × 10 ¹⁷ cm ⁻³ ) 3 layers of Al _0.15 Ga _0.75 As barrier layer (thickness of each layer: 215Å, 79Å, 215Å from the substrate 21 side) and 2 layers of In Multiple strain quantum well active layer 25 formed by alternately stacking _0.12 Ga _0.88 As quantum well layers (thickness of each layer: 46 mm), p-type Al _0.4 Ga _0.6 As second light guide layer 26 (thickness: 0.0. 1 μm, Zn doped: 4.0 × 10 ¹⁷ cm ⁻³ ), p-type Al _0.5 Ga _0.5 As upper first cladding layer 27 (thickness: 0.18 μm, Zn doped: 8.0 × 10 ¹⁷ cm ⁻³ ) , I-type 1st Ga As semiconductor layer 28 (thickness: 150 mm), i-type In _0.245 Ga _0.755 As _0.54 P _0.46 etch stop layer 29 (thickness: 250 mm), n-type Al _0.6 Ga _0.4 As current blocking layer 30 (thickness: 0.8 μm) , Si doping: 2.15 × 10 ¹⁸ cm ⁻³ ) and n-type GaAs protective layer 31 (thickness: 100 mm, Si doping: 2.4 × 10 ¹⁸ cm ⁻³ ) successively grown by MOCVD Let

Next, as shown in FIG. 3, stripe-shaped grooves 33 are formed in the n-type GaAs protective layer 31, the n-type AlGaAs current blocking layer 30, and the i-type InGaAsP etch stop layer 29 by etching using a photolithography technique. Form. Reference numeral 32 denotes a resist mask formed by the photolithography technique. In the etching, an H ₂ SO ₄ based etchant is used to etch the n-type GaAs protective layer 31 and the n-type AlGaAs current blocking layer 30 in a stripe shape. The i-type InGaAsP etch stop layer 29 is hardly etched with an H ₂ SO ₄ etchant. Thereafter, the InGaAsP etch stop layer 29 is removed using a 1: 3 mixed solution of HCl and H ₃ PO ₄ . At that time, as will be described later in detail, a slight over-etching is performed. Through these steps, the stripe-shaped groove 33 can be formed with good reproducibility. In the present embodiment, the width of the bottom portion of the stripe-shaped groove 33 is about 2.5 μm. The resist mask 32 is removed after etching.

Subsequently, as shown in FIG. 4, the p ⁺ -type second GaAs semiconductor layer 34 (thickness: 50 mm, Zn doping: 5 × 10 ¹⁹ cm is formed on the n-type GaAs protective layer 31 and in the trench 33 by MOCVD. ^-3 ) Re-grow. Subsequently, the p-type Al _0.5 Ga _0.5 As upper second cladding layer 35 (thickness: 1.28 μm, Zn doping: 2.4 × 10 ¹⁸ cm ⁻³ ), the p-type GaAs contact layer 36 (thickness: 4.45 μm). Zn doped: 3 × 10 ¹⁸ cm ⁻³ ) and p ⁺ -type GaAs contact layer 37 (thickness: 0.3 μm, Zn doped: 1 × 10 ²⁰ cm ⁻³ ) are successively regrown by MOCVD. . At this time, the growth temperature of the p ⁺ -type second GaAs semiconductor layer 34 is 550 ° C. Thereafter, the growth temperature of the p-type Al _0.5 Ga _0.5 As upper second cladding layer 35 is 685 ° C.

As a result of the above regrowth process, in the current injection region where the first GaAs semiconductor layer 28 and the second GaAs semiconductor layer 34 are in close contact, the Zn dopant contained in the p ⁺ -type second GaAs semiconductor layer 34 is the i-type first GaAs semiconductor. The first GaAs semiconductor layer 28 is diffused to the layer 28 side to be p-type in the current injection region. At that time, the doping concentration of the first GaAs semiconductor layer 28 in the region was about 1 × 10 ¹⁸ cm ⁻³ .

Thus, after the re-growth is completed, Ti (thickness: 1000 mm) / Pt (thickness: 500 mm) / Au (thickness: thickness) is formed on the p ⁺ -type GaAs contact layer 37 by using an electron beam evaporation method. 3000 p) are sequentially stacked to form the p-side electrode 39. Further, after grinding the back surface side of the GaAs substrate 21 to a desired thickness, the back surface side of the GaAs substrate 21 is made of AuGe (thickness: 1500 mm) / Ni (thickness) as the n-side electrode 38 by resistance heating vapor deposition. S: 150 Å) / Au (thickness: 3000 順次) are sequentially stacked and heated in a nitrogen atmosphere at 400 ° C. for 1 minute to perform alloying treatment of the electrode material. Thus, the semiconductor laser element in the present embodiment is completed.

  After dividing the semiconductor laser element thus obtained into a chip size having a desired resonator length, coating both ends with a reflection film (not shown) can function as a semiconductor laser element with an oscillation wavelength of 890 nm. It can be done.

  The semiconductor laser device according to the present embodiment is characterized in that a semiconductor layer (etch stop layer 29) made of InGaAsP is formed before the second cladding layer 35 on the p-type AlGaAs is regrown. As in the case of the conventional semiconductor laser device shown in FIGS. 10 to 12, the mixed crystal ratio of P in the V group of the material is small as compared with the case where the InGaP layer (second etching stop layer 7) is formed. Therefore, the etching rate with the hydrochloric acid-based etchant decreases, and side etching with respect to the AlGaAs layer (current blocking layer 30) is suppressed. Accordingly, it is difficult to form an eaves step on the side surface of the stripe-shaped groove 33.

  In the structure of the conventional semiconductor laser device shown in FIGS. 10 to 12, in order to suppress the side etching of the AlGaAs current confinement layer 8, the InGaP second etching stop layer 7 is etched at a slow etching rate. In such a case, a passive layer that is difficult to be etched and has a high resistance may be formed in the vicinity of the interface with the GaAs semiconductor layer (the GaAs first etching blocking layer 6). However, by forming the InGaAsAs semiconductor layer 29 as in the present embodiment, the side etching can be suppressed while eliminating the above-described problems of formation of the passive layer and high resistance. Therefore, disorder of crystallinity during the regrowth process can be prevented, and deterioration of element resistance can be eliminated. Also, there is an effect that desired optical confinement characteristics can be easily obtained. Furthermore, InGaAsP materials do not have the problem of natural superlattice formation. For this reason, there is no problem of deviation of optical confinement characteristics due to a change in refractive index caused by natural superlattice.

  In the present embodiment, the second GaAs semiconductor layer 34 is formed at the beginning of the regrowth process, but of course the second GaAs semiconductor layer 34 may be omitted. FIG. 5 shows a cross-sectional view of a modification in which the second GaAs semiconductor layer 34 is not provided. Even in the case where the second GaAs semiconductor layer is not formed as in this modification, the above-described deterioration of the element resistance, disorder of regrown crystallinity, and fluctuation of the refractive index due to natural superlattice formation can be prevented. However, by forming the second GaAs semiconductor layer 34 at the beginning of the regrowth process as in the present embodiment, the first GaAs semiconductor layer 28 and the second GaAs semiconductor layer are formed in the current injection region, which is the region in the stripe-shaped groove 33. Since the same kind of material 34 forms a regrowth interface, an effect of further reducing the interface resistance can be added.

  In addition, when the second GaAs semiconductor layer 34 is regrown by the MOCVD method, the growth is performed at a relatively low temperature of 600 ° C. or lower, so that the base of the crystal regrowth exposed from the stripe-shaped groove 33 can be obtained. Re-evaporation of the semiconductor material and dopant from each layer can be suppressed. Therefore, deterioration of element characteristics can be prevented. If re-evaporation occurs during regrowth, the resistance at the interface deteriorates, and the flatness (roughness) of the regrowth interface deteriorates and becomes an absorption loss component due to scattering during laser oscillation operation. Will be lowered.

  Here, in the present embodiment, the first GaAs semiconductor layer 28 is undoped (i-type), but may be p-type. In that case, by providing the second GaAs semiconductor layer 34 grown at a low temperature, the re-evaporation of the dopant from the first GaAs semiconductor layer 28 described above can be suppressed, and deterioration of the element resistance can be prevented. Furthermore, by forming the second GaAs semiconductor layer 34 by low temperature growth, it is possible to suppress the re-evaporation of P from the etch stop layer 29 made of InGaAsP exposed on the side surface of the stripe groove 33. This eliminates the roughening of the regrowth interface, and coupled with the small side etching that is the merit of using the InGaAsP material, it is possible to obtain a good regrowth crystal and achieve high efficiency.

  When the second GaAs semiconductor layer 34 is omitted as in the modification shown in FIG. 5, the second cladding layer 35 on the p-type AlGaAs is started to grow from a relatively low temperature (about 600 ° C.) and the temperature is increased. Re-evaporation can be suppressed by performing growth while raising the value.

In the present embodiment, the second GaAs semiconductor layer 34 is formed in a highly doped state of 5 × 10 ¹⁹ cm ⁻³ . When such a highly doped layer is provided at the beginning of the regrown crystal layer, Zn as a dopant easily diffuses to the substrate 21 side beyond the interface. Therefore, there is an effect of reducing the interface resistance. On the other hand, when the diffusion of Zn proceeds to the vicinity of the active layer 25, there is a concern that the optical characteristics fluctuate and the reliability decreases. However, as in the present embodiment, by using the first GaAs semiconductor layer 28 as an undoped layer having a thickness of 150 mm, the first GaAs semiconductor layer 28 serves as a diffusion preventing layer that blocks diffusion of Zn in the direction of the active layer 25. Can act. This effect can be obtained if the thickness of the undoped first GaAs semiconductor layer 28 in the current injection region is 40 mm or more. In particular, when a high temperature operation or a high output operation is performed, it is desirable that it is about 100 mm or more. As described above, through the thermal history in the regrowth process, Zn dopant diffuses from the heavily doped second GaAs semiconductor layer 34 to the first GaAs semiconductor layer 28 side in the current injection region, The first GaAs semiconductor layer 28 is p-type. Furthermore, as described above, by setting the thickness of the first GaAs semiconductor layer 28 to 150 mm, Zn dopant does not diffuse beyond the first GaAs semiconductor layer 28.

  By adopting such a configuration, it is possible to obtain a good semiconductor laser element that does not vary in optical characteristics or decrease in reliability while lowering the interface resistance. However, since an element resistance increases if a too thick undoped layer is present in the current injection region, it is desirable that the thickness of the undoped layer be up to 200 mm. This is because the Zn dopant supplied from the second GaAs semiconductor layer 34 after the above-described regrowth process diffused only to a depth of about 200 mm at the maximum. That is, when an undoped layer exceeding 200 Å is formed, the undoped layer having a high resistance remains thick even after the diffusion of the Zn dopant occurs. Of course, this is not the case when the element resistance is not important. This effect is particularly effective for a semiconductor laser device having an oscillation wavelength of 870 nm or more. In the case of a 780 nm band semiconductor laser device used for a compact disk or the like, the thickness of the undoped GaAs semiconductor layer may be preferably suppressed to about 40 mm or less in consideration of light absorption.

  In the semiconductor laser device of the present embodiment, the thickness of the first GaAs semiconductor layer 28 in the current injection region is slightly thinner than that in the current non-injection region (not shown in the drawing). This removes the InGaAsP etch stop layer 29 from the very thin interface layer containing P due to the interface sag during crystal growth existing at the interface between the first GaAs semiconductor layer 28 and the InGaAs AsP etch stop layer 29 thereover. This is because it is removed by over-etching. As described above, by performing crystal regrowth of the second GaAs semiconductor layer 34 and the like after removing the interface layer containing P, a good regrowth crystal quality can be obtained. Therefore, the resistance at the interface can be reduced, the resistance in the regrowth crystal layer can be reduced, and the composition can be stabilized, and the device characteristics can be improved. Further, since the layer formed on the first GaAs semiconductor layer 28 is the InGaAsP layer 29 having a P mixed crystal ratio in the V group smaller than that of InGaP, there is no formation of a passive layer that is difficult to be etched as described above. This makes it easy to remove the very thin interface layer containing P formed in the film.

  At that time, the P mixed crystal ratio in the group V element in the InGaAsP layer 29 is preferably 0.4 or more and 0.6 or less. If the P mixed crystal ratio is 0.4 or more, the InGaAsAs layer 29 has sufficient etching selectivity with respect to the n-type AlGaAs current blocking layer 30, and the first GaAs semiconductor layer 28 and the InGaAsAsP layer 29 The interface layer containing very thin P formed at the interface can be easily removed. Furthermore, if the mixed crystal ratio of P is 0.6 or less, side etching for the AlGaAs current blocking layer 30 is sufficiently suppressed, and sufficient etching selectivity for the first GaAs semiconductor layer 28 is ensured. it can. Furthermore, it is possible to prevent the formation of a passive layer which is difficult to be etched at the interface and which has a high resistance.

  In the semiconductor laser device of the present embodiment, the InGaAsAsP etch stop layer 29 is intrinsic (i-type). In this way, by making it intrinsic, there is no problem of diffusion of the dopant contained in the InGaAsAsP etch stop layer 29 itself, and the second conductivity type (n-type) AlGaAs current blocking layer formed thereon is formed. 30 can act as a diffusion preventing layer for the dopant contained in 30. This also has the effect of suppressing changes in optical characteristics and a decrease in reliability. Further, the InGaAsP etch stop layer 29 may be of the second conductivity type (p-type). In this case, the dopant diffusion of the p-type InGaAsP etch stop layer itself is covered by the intrinsic first GaAs semiconductor layer 28. On the other hand, since the InGaAsP etch stop layer is doped to the second conductivity type, diffusion of the first conductivity type dopant of the n-type AlGaAs current blocking layer 30 provided on the p-type InGaAsAsP etch stop layer is performed. There is an effect to prevent.

In the semiconductor laser device of this embodiment, the P mixed crystal ratio in the group V element in the i-type InGaAsAsP etch stop layer 29 is 0.46. As described above, when the P mixed crystal ratio is set to 0.4 or more and 0.6 or less, by using a mixed etchant of HCl and H ₃ PO ₄ , an InGaP material is used as the etch stop layer. In contrast, while suppressing the amount of side etching with respect to the AlGaAs current blocking layer 30, the interface layer containing P formed at the interface between the InGaAsAs layer 29 and the first GaAs semiconductor layer 28 in the etching process of the InGaAsAsP etch stop layer 29 is removed. It becomes possible. Therefore, the crystal quality in the subsequent regrowth process can be improved and the interface resistance can be reduced. In this case, as described above, if the mixed crystal ratio of P in the group V element exceeds 0.6, the effect of suppressing the side etching and the effect of preventing the formation of the passive layer are lost, and it is less than 0.4. The selective etching property is deteriorated, and the interface layer containing P cannot be removed.

  In the semiconductor laser device of the present embodiment, the Al mixed crystal ratio 0.6 in the group III element in the current blocking layer 30 made of n-type AlGaAs has an upper second cladding layer 35 made of p-type AlGaAs. Since the Al mixed crystal ratio in the group III element is larger than 0.5, it is possible to realize a real guide type semiconductor laser device with little optical loss. Therefore, an effect that the oscillation threshold can be reduced can be achieved.

In the method of manufacturing the semiconductor laser device according to the present embodiment, the first GaAs semiconductor is used when the removal of the InGaAsP etch stop layer 29 in the step of forming the stripe groove 33 is performed with a mixed solution of HCl and H ₃ PO _4. Some over-etching is applied after layer 28 is exposed. In this case, since the P mixed crystal ratio in the group V element in the InGaAsP etch stop layer 29 is 0.4 or more and 0.6 or less, the interface containing P formed at the interface between the InGaAsP layer 29 and the GaAs layer 28. The layer can be easily removed. By adding such a process of “removing the interface layer containing P”, the surface of the pure GaAs material can be exposed, and the quality of the regrowth crystal formed thereafter can be improved. In addition, as a result of removing the interface layer containing P, the internal roughness is reduced by improving the roughness of the interface, so that the oscillation threshold current value and the oscillation efficiency can be improved.

  Further, by forming the second GaAs semiconductor layer 34 at a relatively low temperature at the beginning of the regrowth process, the semiconductor material and dopant are regenerated from each semiconductor layer that is the foundation of crystal regrowth exposed from the stripe-shaped groove 33. Evaporation can be suppressed. In this case, when the growth temperature of the second GaAs semiconductor layer 34 is lower than 500 ° C., the growth mechanism of the GaAs semiconductor layer is different from the case where the growth mechanism is 500 ° C. or higher. The crystallinity may be reduced. Moreover, when it exceeds 600 degreeC, the effect which suppresses re-evaporation decreases. Therefore, 500 to 600 ° C. is preferable.

  After that, by re-growing the upper second cladding layer 35 made of AlGaAs at a relatively high temperature, it is possible to prevent oxygen from being taken into the AlGaAs layer during the regrowth process. In this case, the growth temperature of the AlGaAs upper second cladding layer 35 is preferably at least 650 ° C. or higher. In general, when an Al-containing layer is oxidized, a deep order is formed and light absorption occurs in that portion, so that the reliability of the device is lowered. Further, the characteristics of the laser device such as the oscillation threshold current value and the oscillation efficiency are reduced. Will get worse. By using the manufacturing method as described above, re-evaporation of the semiconductor material or dopant from the substrate 21 side can be suppressed while preventing oxygen from being taken into the Al-containing layer in the regrowth process. Therefore, it is possible to provide a method for manufacturing a semiconductor laser device having good characteristics that has low internal loss (absorbing component) and has both low device resistance and high reliability.

  In the present embodiment, the case where the present invention is applied to a semiconductor laser element having an oscillation wavelength band of 890 nm is described as an example, but the present invention is not limited to this. For example, it goes without saying that the present invention can be applied to semiconductor laser elements in other oscillation wavelength bands such as the 780 nm band and the 650 nm band.

Further, in the above embodiment, crystal growth from the n-type GaAs buffer layer 22 to the n-type GaAs protective layer 31, and re-growth from the p ⁺ type first 2GaAs semiconductor layer 34 to the p ⁺ -type GaAs contact layer 37 Is performed by the MOCVD method. However, the present invention is not limited to this and may be performed by the MBE method.

Second Embodiment The present embodiment relates to an optical transmission module using the semiconductor laser element in the first embodiment and an optical transmission system using the optical transmission module. FIG. 6 is a cross-sectional view showing the light transmission module 51. FIG. 7 is a perspective view showing a light source portion in FIG.

  In the present optical transmission module 51, the InGaAs semiconductor laser element (laser chip) 52 having the oscillation wavelength of 890 nm described in the first embodiment is used as a light source. As the light receiving element 53, a silicon (Si) pin photodiode is used. In the above optical transmission system, it is assumed that the other party that transmits and receives signals also includes the same optical transmission module 51.

  In FIG. 6, a pattern (not shown) of both positive and negative electrodes for driving a semiconductor laser is formed on a circuit board 54, and a recess 54a having a depth of 300 μm is provided in a portion where the laser chip 52 is mounted. ing. The bottom of the recess 54a is flat, and a laser mount (mounting material) 55 on which the laser chip 52 is mounted is fixed on the flat portion with solder. The flat portion 57 (see FIG. 7) of the positive electrode 56 of the laser mount 55 is electrically connected to a laser driving positive electrode portion (not shown) on the circuit board 54 by a wire 58a. The recess 54a has a depth that does not hinder the emission of laser light, and the roughness of the surface does not affect the emission angle.

  The light receiving element 53 is mounted on the circuit board 54 in the same manner as the laser mount 55, and an electric signal is taken out by a wire 58b. In addition to this, an IC circuit (integrated circuit) 59 for laser driving and reception signal processing is mounted on the circuit board 54.

  The laser mount 55 mounted in the recess 54 a of the circuit board 54 is sealed with a silicon resin 60. In this resin sealing, an appropriate amount of a liquid silicon resin 60 is dropped on a portion of the recess 54a where the laser mount 55 is fixed on the circuit board 54, and is heated at 80 ° C. for about 5 minutes to be cured into a jelly shape. Done. The silicon resin 60 dropped as described above remains in the recess 54a due to surface tension, covers the laser mount 55, and is fixed to the recess 54a. In the present embodiment, a recess 54a is provided on the circuit board 54, and a laser mount 55 is mounted in the recess 54a. However, the silicon resin 60 is applied to the surface of the laser chip 52 and its vicinity by surface tension. Since it stays, the recessed part 54a does not necessarily need to be provided.

  Further, the entire circuit board 54 is covered with a transparent epoxy resin mold 61. At this time, a lens portion 62 for controlling the emission angle is formed on the upper surface of the laser chip 52, and a lens portion 63 for condensing the signal light is formed on the upper surface of the light receiving element 53. The lens unit 62 and the lens unit 63 are integrated to form a molded lens.

  Next, the laser mount 55 will be described in detail with reference to FIG. In FIG. 7, the laser chip 52 is die-bonded to the vertical portion 64a of an L-shaped heat sink 64 using In glue. Here, the laser chip 52 is the InGaAs-based semiconductor laser element in the first embodiment, and the chip lower surface 52b is coated with a high reflection film (not shown), while the chip upper surface 52a is low reflection. A membrane (not shown) is coated. These reflective films also serve as protection for the end face of the laser chip 52.

  The positive electrode 56 is fixed to the base portion 64 b of the heat sink 64 with an insulator so that the positive electrode 56 is not electrically connected to the heat sink 64. The positive electrode 56 and the p-side electrode 52c on the surface of the laser chip 52 are connected by a gold wire 58c. As shown in FIG. 6, the laser mount 55 having the above configuration is fixed to the negative electrode (not shown) formed on the flat portion of the concave portion 54 a of the circuit board 54 with solder, while the flat portion on the positive electrode 56 is flat. The portion 57 and a positive electrode portion for laser driving (not shown) on the circuit board 54 are connected by a wire 58a. By wiring in this way, the optical transmission module 51 capable of obtaining the laser beam 65 by oscillation is completed.

  FIG. 8 is a schematic view of an optical transmission system using the optical transmission module 51. As described above, in this optical transmission system, it is assumed that the other party holds the same optical transmission module 51 and transmits and receives an optical signal. The optical transmission system shown in FIG. 8 performs data communication using light (infrared rays) between the personal computer 71 and the base station 72.

  An optical transmission module 51 having the configuration shown in FIGS. 6 and 7 is mounted on the operation surface of the personal computer 71 with the light emitting surface and the light receiving surface facing upward. The base station 72 is installed on the ceiling of the room, and an optical transmission module (not shown) 51 having the configuration shown in FIGS. 6 and 7 is mounted with the light emitting surface and the light receiving surface facing downward. Yes. By using the personal computer 71 as a terminal and the base station 72 server, data communication using light (infrared rays) is performed.

  For example, signal light (laser light on which a data signal is superimposed) representing specific information is emitted from the light source (laser chip 52) of the light transmission module 51 mounted on the personal computer 71. Then, this signal light is received by the light receiving element 53 of the optical transmission module 51 mounted on the base station 72. Similarly, the signal light transmitted from the base station 72 is received by the light receiving element 53 on the personal computer 71 side.

  In that case, the optical transmission module 51 in the present embodiment does not deteriorate the resistance value at the interface portion of the regrowth film as described above, and further uses a highly reliable semiconductor laser element. The power consumption of the module 51 can be kept lower than that of the conventional optical transmission module. That is, according to the present embodiment, it is possible to provide an optical transmission system that is energy saving and has a smaller load on the environment and has a long life. Further, when the present optical transmission system is mounted on a portable device or the like, the operation time can be extended as compared with the conventional optical transmission system.

Third Embodiment The present embodiment relates to an optical disc apparatus using the semiconductor laser element in the first embodiment. FIG. 9 is a configuration diagram of the optical disc apparatus according to the present embodiment. This optical disc apparatus writes data on the optical disc 81 or reproduces data written on the optical disc 81, and includes the semiconductor laser element 82 in the first embodiment as a light emitting element used at that time. ing.

  Hereinafter, the configuration and operation of the optical disc apparatus will be described. In the present optical disc apparatus, when writing, the signal light emitted from the semiconductor laser element 82 (laser light on which the data signal is superimposed) passes through the collimator lens 83 to become parallel light and passes through the beam splitter 84. Then, after the polarization state is adjusted by the λ / 4 polarizing plate 85, the light is condensed by the laser light irradiation objective lens 86 to irradiate the optical disk 81. In this way, data is written on the optical disc 81 by the laser beam on which the data signal is superimposed.

  On the other hand, at the time of reading, the optical disc 81 is irradiated with a laser beam emitted from the semiconductor laser element 82 on which the data signal is not superimposed following the same path as in the case of the writing. Then, the laser beam reflected by the surface of the optical disk 81 on which the data is recorded passes through the objective lens 86 for irradiating the laser beam and the λ / 4 polarizing plate 85 and then is reflected by the beam splitter 84 to change the traveling direction by 90 °. Is done. Thereafter, the light is condensed by a reproduction light objective lens 87 and is incident on a signal detection light receiving element 88. In this way, the data signal read from the optical disk 81 is converted into an electric signal in accordance with the intensity of the incident laser beam in the signal detecting light receiving element 88, and is reproduced into the original information signal by the signal light reproducing circuit 89. It is.

  In the optical disk device according to the present embodiment, as described above, the semiconductor laser element 82 that does not deteriorate the resistance value at the interface portion of the regrowth film and has high reliability is used. Therefore, the power consumption of the optical disk device can be kept lower than that of the conventional optical disk device.

  The semiconductor laser device, the manufacturing method of the semiconductor laser device, the optical transmission system, and the optical disc apparatus of the present invention are the semiconductor laser device and the manufacturing method thereof in the first embodiment, the optical transmission system in the second embodiment, Further, the present invention is not limited to the optical disk device in the third embodiment. For example, various changes can be made, for example, within the range not departing from the gist of the present invention, such as the thickness and number of layers of the well layers and barrier layers.

It is sectional drawing in the semiconductor laser element of this invention. FIG. 2 is a cross-sectional view of the semiconductor laser element shown in FIG. 1 during the manufacturing process. FIG. 3 is a cross-sectional view during the manufacturing process subsequent to FIG. 2. FIG. 4 is a cross-sectional view during the manufacturing process subsequent to FIG. 3. FIG. 2 is a cross-sectional view of a semiconductor laser device different from FIG. It is sectional drawing of the optical transmission module using the semiconductor laser element shown in FIG. It is a perspective view which shows the part of the light source in FIG. 1 is an overview of an optical transmission system according to the present invention. It is a block diagram of the optical disk apparatus of this invention. It is sectional drawing in the manufacturing process of the conventional semiconductor laser element. It is sectional drawing in the manufacturing process following FIG. It is sectional drawing in the manufacturing process following FIG.

Explanation of symbols

21 ... n-type GaAs substrate,
22 ... n-type GaAs buffer layer,
23: n-type AlGaAs lower cladding layer,
24 ... n-type AlGaAs first light guide layer,
25. Multiple quantum well active layer,
26 ... p-type AlGaAs second light guide layer,
27... First clad layer on p-type AlGaAs
28 ... i-type first GaAs semiconductor layer partially p-type,
29 ... i-type InGaAsP etch stop layer,
30 ... n-type AlGaAs current blocking layer,
31 ... n-type GaAs protective layer,
33 ... Groove,
34... P ⁺ type second GaAs semiconductor layer,
35... Second clad layer on p-type AlGaAs
36 ... p-type GaAs contact layer,
37 ... p ⁺ -type GaAs contact layer,
38 ... n-side electrode,
39 ... p-side electrode,
51. Optical transmission module,
52. InGaAs-based semiconductor laser element (laser chip),
53. Light receiving element,
54 ... Circuit board,
55 ... Laser mount,
56: Positive electrode,
60 ... Silicone resin,
61 ... Epoxy resin mold,
62, 63 ... lens part,
64 ... heat sink,
65 ... Laser beam,
71 ... Personal computer,
72 ... Base station,
81 ... optical disc,
82: Semiconductor laser element,
83 ... collimating lens,
84: Beam splitter,
85 ... λ / 4 polarizing plate,
86 ... Objective lens for laser light irradiation,
87 ... Objective lens for reproduction light,
88. Light receiving element for signal detection,
89 ... Signal light regeneration circuit.

Claims (17)

In a semiconductor laser device in which at least a first conductivity type lower cladding layer, an active layer, a second conductivity type upper first cladding layer, and a first GaAs semiconductor layer are sequentially stacked on a first conductivity type GaAs substrate.
A current injection region and a current non-injection region are provided on the first GaAs semiconductor layer,
In the current non-injection region, at least an InGaAsAs semiconductor layer and a first conductivity type AlGaAs semiconductor layer are formed,
A semiconductor laser element, wherein a second conductivity type AlGaAs upper second cladding layer is formed on the InGaAsP semiconductor layer or AlGaAs semiconductor layer in the current non-injection region and in the current injection region. . The semiconductor laser device according to claim 1,
A second GaAs semiconductor layer is formed on the InGaAsP semiconductor layer or the AlGaAs semiconductor layer in the current non-injection region, and in the current injection region, below the AlGaAs upper second cladding layer, and the current injection region. Wherein the first GaAs semiconductor layer and the second GaAs semiconductor layer are in close contact with each other. The semiconductor laser device according to claim 2,
The semiconductor laser device, wherein the first GaAs semiconductor layer and the second GaAs semiconductor layer are of a second conductivity type. The semiconductor laser device according to claim 3,
The semiconductor laser device, wherein the first GaAs semiconductor layer is of a second conductivity type having a doping concentration lower than that of the second GaAs semiconductor layer. The semiconductor laser device according to claim 4,
The second GaAs semiconductor layer is of a second conductivity type using Zn as a dopant. The semiconductor laser device according to claim 5, wherein
A thickness of the first GaAs semiconductor layer in the current injection region is 40 to 200 mm. The semiconductor laser device according to claim 1,
The semiconductor laser device, wherein a thickness of the first GaAs semiconductor layer in the current injection region is smaller than a thickness of the current non-injection region. The semiconductor laser device according to claim 1,
A semiconductor laser element, wherein the InGaAsP semiconductor layer is intrinsic or of a second conductivity type. The semiconductor laser device according to claim 1,
A semiconductor laser device, wherein a mixed crystal ratio of P in the group V element in the InGaAsAs semiconductor layer is 0.4 or more and 0.6 or less. The semiconductor laser device according to claim 1,
A semiconductor laser device, wherein an Al mixed crystal ratio in a group III element in the AlGaAs semiconductor layer is larger than an Al mixed crystal ratio in a group III element in the AlGaAs upper second cladding layer. In a method of manufacturing a semiconductor laser device, wherein at least a first conductivity type lower cladding layer, an active layer, and a second conductivity type upper first cladding layer are sequentially laminated on a first conductivity type GaAs substrate.
Crystal-growing a first GaAs semiconductor layer, an InGaAsAs semiconductor layer, and a first conductivity type AlGaAs semiconductor layer on the upper first cladding layer;
Removing a part of the AlGaAs semiconductor layer to form a current injection region;
Removing the InGaAsP semiconductor layer in the current injection region to partially expose the first GaAs semiconductor layer;
Removing the surface portion of the exposed portion of the first GaAs semiconductor layer to a predetermined depth;
A method of manufacturing a semiconductor laser device, comprising a step of crystal regrowth of an upper second cladding layer of a second conductivity type at least in the current injection region. In the manufacturing method of the semiconductor laser device according to claim 10,
After the surface portion of the exposed portion of the first GaAs semiconductor layer is removed to a predetermined depth and before the upper second cladding layer is regrown, the second GaAs semiconductor layer is crystallized at least in the current injection region. A method of manufacturing a semiconductor laser device, comprising a step of regrowth. In the manufacturing method of the semiconductor laser device according to claim 11,
The first GaAs semiconductor layer is intrinsic, while the second GaAs semiconductor layer is of a second conductivity type,
A method of manufacturing a semiconductor laser device, wherein when the second GaAs semiconductor layer is crystal regrown, the first GaAs semiconductor layer is converted to a second conductivity type by diffusion of a dopant from the second GaAs semiconductor layer. In the manufacturing method of the semiconductor laser device according to claim 11,
A method of manufacturing a semiconductor laser device, wherein crystal regrowth of the second GaAs semiconductor layer is performed using a metal organic chemical vapor deposition method. In the manufacturing method of the semiconductor laser device according to claim 13,
A method of manufacturing a semiconductor laser device, wherein the growth temperature of the second GaAs semiconductor layer is 500 ° C. or higher and 600 ° C. or lower.   An optical transmission system using the semiconductor laser device according to claim 1. An optical disk apparatus using the semiconductor laser element according to claim 1.

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