JP2009117551A - Semiconductor laser device and manufacturing method thereof - Google Patents

Abstract

In a semiconductor laser device having a semiconductor whose active layer has a large influence on the laser characteristics due to oxidation as an active layer, a semiconductor laser device capable of obtaining a gain-coupled DFB structure without processing the active layer and a manufacturing method thereof are provided. .
A semiconductor laser device includes an n-type semiconductor substrate including a III-V compound semiconductor, an n-type cladding layer provided on the semiconductor substrate, and an active layer. 11 includes a semiconductor laminated portion 12 provided on the semiconductor laminated portion 12 and a p-type cladding layer 13 provided on the semiconductor laminated portion 12. The semiconductor stacked unit 12 includes a plurality of light absorption regions 18 that are arranged along the active layer 15 in a cycle corresponding to a predetermined wavelength and absorb light having a wavelength emitted from the active layer 15. The active layer 15 is made of a III-V group compound semiconductor containing Al in the composition. The plurality of light absorption regions 18 are made of a group III-V compound semiconductor that does not substantially contain Al.
[Selection] Figure 1

Description

  The present invention relates to a semiconductor laser device and a manufacturing method thereof.

In Patent Document 1, in a distributed feedback (DFB) laser element, a concave portion of a diffraction grating formed in an active layer is filled with a buried layer having a refractive index higher than that of a cladding layer, and the convex portion of the active layer and the buried portion of the diffraction grating are buried. A technique for covering the buried layer with a cladding layer is described. Thereby, the refractive index coupling component and the gain coupling component are generated in phase in the light guiding direction.
JP 2004-55797 A

  In the DFB laser element described in Patent Document 1, a diffraction grating is formed by etching an active layer. In this case, the active layer is exposed in the step of forming the diffraction grating, and the active layer surface is easily oxidized. There is no problem when the active layer is a semiconductor (for example, GaInAsP) that has little influence on the laser characteristics due to oxidation, but there is a patent when the semiconductor (for example, AlGaInAs) that has a large influence on the laser characteristics due to oxidation is the active layer. The configuration described in Document 1 cannot be adopted. Further, since it is necessary to perform fine processing by etching on the active layer when forming the diffraction grating, there is a possibility that the active layer is damaged by this fine processing, non-radiative recombination increases, and laser characteristics are deteriorated. .

  The present invention has been made in view of the above-described problems, and in a semiconductor laser device using a semiconductor whose active layer has a large influence on the laser characteristics due to oxidation as an active layer, a gain-coupled DFB structure is formed without processing the active layer. It is an object of the present invention to provide a semiconductor laser device that can be obtained and a manufacturing method thereof.

  In order to solve the above-described problems, a semiconductor laser device according to the present invention is a semiconductor laser device that outputs laser light having a predetermined wavelength, and includes a semiconductor substrate of a first conductivity type including a III-V compound semiconductor, and a semiconductor. A first conductivity type cladding layer provided on the substrate; a semiconductor laminated portion having an active layer and provided on the first conductivity type clad layer; a second conductivity type cladding layer provided on the semiconductor laminate portion; The semiconductor laminated portion is arranged along the active layer in a cycle corresponding to a predetermined wavelength, and further includes a plurality of light absorption regions that absorb light having a wavelength emitted by the active layer, and the active layer is in the composition And a plurality of light absorption regions are made of a group III-V compound semiconductor that does not substantially contain Al.

  The active layer of the semiconductor laser element described above is made of a III-V group compound semiconductor containing Al in the composition, and the influence of the oxidation on the laser characteristics is great. In the semiconductor laser device described above, a plurality of light absorption regions that absorb light having a wavelength emitted from the active layer are arranged along the active layer at a period corresponding to a predetermined wavelength to be output. Thereby, the light absorption characteristic in the optical waveguide direction periodically changes. As a result, the gain also changes periodically, and a gain-coupled DFB laser device can be suitably realized. Further, when forming such a light absorption region, it is not necessary to process the active layer. That is, according to this semiconductor laser device, a gain-coupled DFB structure can be easily obtained without processing the active layer.

  The semiconductor laser element may further include an intermediate semiconductor region having a lower refractive index than the plurality of light absorption regions between the plurality of light absorption regions. By filling the space between the plurality of light absorption regions with a semiconductor having a lower refractive index than the light absorption region, a periodic refractive index distribution can be formed in the direction along the active layer. Thereby, a refractive index coupling component and a gain coupling component are generated in the light guiding direction, and a more stable single mode operation and low threshold current operation can be realized by their synergistic effect (complex coupling).

  A method of manufacturing a semiconductor laser device according to the present invention is a method of manufacturing a semiconductor laser device that outputs laser light of a predetermined wavelength, and is formed on a first conductivity type semiconductor substrate containing a III-V group compound semiconductor. A first clad layer forming step for forming a one-conductivity-type clad layer; a laminate-unit forming step for forming a semiconductor laminate having an active layer on the first-conductivity-type clad layer; and a second conductive-type clad layer as a semiconductor laminate A second clad layer forming step formed on the portion, and the laminated portion forming step includes forming an active layer by growing a III-V group compound semiconductor containing Al in the composition, and an active layer forming step A III-V group compound semiconductor that absorbs light having a wavelength emitted from the layer and that does not substantially contain Al is grown, and then has a plurality of mask patterns periodically arranged on the group III-V compound semiconductor. Using a mask A light absorption region forming step of forming a plurality of light absorption regions arranged along the active layer at a period corresponding to a predetermined wavelength by etching the III-V compound semiconductor.

  In the semiconductor laser device manufacturing method described above, an active layer is formed by growing a III-V group compound semiconductor containing Al in the composition in the active layer forming step. Therefore, this active layer has a great influence on the laser characteristics due to oxidation. In the manufacturing method described above, in the light absorption region forming step, a plurality of light absorption regions arranged along the active layer are formed at a period corresponding to a predetermined wavelength to be output. As a result, the light absorption characteristics in the optical waveguide direction periodically change in the manufactured semiconductor laser device. As a result, the gain also changes periodically, and a gain-coupled DFB laser device can be suitably manufactured. Further, the active layer is not required to be processed in the light absorption region forming step. That is, according to this method of manufacturing a semiconductor laser device, a gain coupled DFB structure can be easily obtained without processing the active layer.

  The method for manufacturing a semiconductor laser device may be characterized in that the layered portion forming step further includes an embedding step of filling a gap between the plurality of light absorption regions with a semiconductor having a lower refractive index than the plurality of light absorption regions. Good. A gap between the plurality of light absorption regions is filled with a semiconductor having a lower refractive index than that of the light absorption region, whereby a periodic refractive index distribution can be formed in a direction along the active layer. As a result, a refractive index coupling component and a gain coupling component are generated in the light guiding direction, and by these synergistic effects (complex coupling), more stable single mode operation and low threshold current operation can be easily realized. .

  Also, in the method of manufacturing the semiconductor laser device, the stacking portion forming step includes a step of filling a gap between a plurality of light absorption regions with a semiconductor, a plurality of light absorption regions, and a semiconductor embedded in the step of filling. And a step of growing a group III-V compound semiconductor containing Al in the composition. For example, when a ridge waveguide type laser element or the like is manufactured, a stripe-shaped ridge structure may be formed by etching the second conductivity type cladding layer until the semiconductor laminated portion is exposed. In such a case, a group III-V compound semiconductor containing Al in the composition is grown on the plurality of light absorption regions and the semiconductor buried in the embedding step, and a second conductivity type cladding layer is formed thereon. Thus, the layer made of a III-V group compound semiconductor containing Al functions as an etch stop layer when the second conductivity type cladding layer is etched. Therefore, a striped ridge structure can be easily formed in the second conductivity type cladding layer.

  Further, in the method for manufacturing a semiconductor laser device, the layered portion forming step grows a III-V group compound semiconductor containing Al in the composition on the active layer between the active layer forming step and the light absorption region forming step. The method may further include a step. Thus, when the III-V group compound semiconductor is etched in the light absorption region forming step, the layer made of the III-V group compound semiconductor containing Al formed on the active layer functions as an etch stop layer. Therefore, it is possible to prevent the etching from reaching the active layer during the light absorption region forming step.

  According to the semiconductor laser device and the manufacturing method thereof according to the present invention, a gain-coupled DFB structure can be obtained without processing an active layer in a semiconductor laser device having an active layer of a semiconductor having a large influence on laser characteristics due to oxidation. Can do.

  Embodiments of a semiconductor laser device and a manufacturing method thereof according to the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective sectional view showing the structure of a semiconductor laser device according to an embodiment of the present invention. 2 is a side cross-sectional view showing a II-II cross section of FIG. The semiconductor laser device 10 of this embodiment outputs laser light having a predetermined wavelength. 1 and 2, the semiconductor laser device 10 includes an n-type (first conductivity type) semiconductor substrate 21 having a main surface 21a. The n-type semiconductor substrate 21 mainly contains a III-V group compound semiconductor, and is made of n-type InP as an example.

  In addition, the semiconductor laser element 10 includes an n-type cladding layer 11, a semiconductor stacked portion 12, a p-type cladding layer 13, and a p-type contact layer 27. The n-type cladding layer 11 is provided on the main surface 21a of the n-type semiconductor substrate 21 and mainly contains a III-V group compound semiconductor. As an example, the n-type cladding layer 11 is made of n-type InP. The layer thickness of the n-type cladding layer 11 is, for example, 2.0 [μm].

  The semiconductor stacked portion 12 includes a first light confinement layer 14, an active layer 15, a second light confinement layer 16, and a diffraction grating layer 17, and is provided on the n-type cladding layer 11. The first optical confinement layer 14 is provided on the n-type cladding layer 11 and mainly includes an n-type III-V group compound semiconductor having a narrower band gap than the n-type cladding layer 11. In one embodiment, the first optical confinement layer 14 is made of n-type AlGaInAs. The layer thickness of the first optical confinement layer 14 is, for example, 70 [nm].

  The active layer 15 is provided on the first optical confinement layer 14 and is made of a III-V group compound semiconductor containing Al in the composition. As an example, the active layer 15 has a multiple quantum well structure, and barrier layers (barrier layers) 15a and well layers 15b made of undoped (that is, not doped with impurities) AlGaInAs are alternately stacked. It consists of The thickness of the barrier layer 15a is, for example, 9 [nm], and the thickness of the well layer 15b is, for example, 6 [nm]. The second optical confinement layer 16 is provided on the active layer 15 and mainly includes a p-type III-V group compound semiconductor having a narrower band gap than the p-type cladding layer 13. In one embodiment, the second optical confinement layer 16 is made of p-type AlGaInAs. The layer thickness of the second optical confinement layer 16 is, for example, 30 [nm].

  The diffraction grating layer 17 is provided on the second optical confinement layer 16. The diffraction grating layer 17 includes a plurality of light absorption regions 18 arranged along the active layer 15 and a carrier stop region 19 formed so as to embed the upper surface, the lower surface, and the side surfaces of the plurality of light absorption regions 18. It consists of

The plurality of light absorption regions 18 are arranged along the active layer 15 with a period corresponding to a predetermined wavelength to be output by the semiconductor laser element 10. Each light absorption region 18 is made of a III-V group compound semiconductor having a composition having substantially the same PL wavelength as the photoluminescence (PL) wavelength of the active layer 15, and absorbs light having a wavelength emitted by the active layer 15. However, the composition of the light absorption region 18 does not substantially contain Al and is different from the composition of the active layer 15 in that respect. In one embodiment, the light absorption region 18 is made of GaInAsP. Further, the light absorption region 18 is doped with at least one of Fe and Ru so as to be semi-insulating so that the light absorption region 18 does not emit light due to absorption of carriers flowing to the active layer 15. When Ru is doped, a suitable concentration is, for example, 2 × 10 ¹⁸ [cm ⁻³ ]. In addition, when Fe is doped, in order to suppress interdiffusion with Zn as a p-type dopant, the preferred concentration is smaller than that when Ru is doped, for example, 6 × 10 ¹⁶ [cm ⁻³ ].

  The plurality of light absorption regions 18 of the present embodiment are formed on the second optical confinement layer 16 with the direction perpendicular to the optical waveguide direction as the longitudinal direction, and are periodically arranged in the optical waveguide direction. The period Λ (see FIG. 2) of the light absorption region 18 is set according to the wavelength of the laser beam to be output. For example, when the wavelength of the laser beam is 1550 [nm], it is set to 240 [nm]. When the wavelength of the laser beam is 1300 [nm], it is set to 200 [nm]. The layer thickness of each light absorption region 18 is, for example, 30 [nm].

  The carrier stop region 19 includes a lower semiconductor region 19a provided between the second light confinement layer 16 and the plurality of light absorption regions 18, an intermediate semiconductor region 19b provided in a gap between the plurality of light absorption regions 18, and An upper semiconductor region 19 c provided between the plurality of light absorption regions 18 and the p-type cladding layer 13 is included. The lower semiconductor region 19a and the upper semiconductor region 19c are made of a p-type III-V group compound semiconductor containing Al in the composition. The intermediate semiconductor region 19b is made of a p-type III-V group compound semiconductor having a lower refractive index than the light absorption region 18. The lower semiconductor region 19a, the intermediate semiconductor region 19b, and the upper semiconductor region 19c may be made of III-V compound semiconductors having the same composition. In one embodiment, these semiconductor regions 19a to 19c are made of p-type AlInAs. The layer thickness of the lower semiconductor region 19a is, for example, 20 [nm], the layer thickness of the intermediate semiconductor region 19b is the same as that of the light absorption region 18 (for example, 30 [nm]), and the layer thickness of the upper semiconductor region 19c is, for example, 20 [Nm].

  The p-type cladding layer 13 is provided on the semiconductor stacked portion 12 (specifically, on the upper semiconductor region 19c of the carrier stop region 19), and has a stripe-shaped ridge structure. That is, the p-type cladding layer 13 has a ridge portion 13a, and this ridge portion 13a extends along the optical waveguide direction. In the semiconductor laser device 10, a refractive index type waveguide is formed by an effective refractive index distribution inside the active layer 15 generated by current injection into the ridge portion 13a. The p-type cladding layer 13 mainly includes a p-type III-V compound semiconductor. As an example, the p-type cladding layer 13 is made of p-type InP. The layer thickness of the p-type cladding layer 13 is, for example, 2.0 [μm].

Both side surfaces of the ridge portion 13a are buried with buried regions 24 made of a nonconductive material such as benzocyclobutene (BCB) resin. An insulating film 25 made of SiO ₂ is provided between the buried region 24 and both side surfaces of the ridge portion 13a. The insulating film 25 of the present embodiment is in contact with the surface of the upper semiconductor region 19c exposed from between the ridge portion 13a and other portions of the p-type cladding layer 13 in addition to both side surfaces of the ridge portion 13a. Further, the buried region 24 and the insulating film 25 also cover other parts of the p-type cladding layer 13.

  The p-type contact layer 27 is provided on the ridge portion 13a of the p-type cladding layer 13, and mainly includes a high-concentration p-type III-V group compound semiconductor. As an example, the p-type contact layer 27 is made of p-type GaInAs. The layer thickness of the p-type cladding layer 13 is, for example, 500 [nm].

  An anode electrode film (not shown) is provided on the p-type contact layer 27 provided on the ridge portion 13a. The anode electrode film and the p-type contact layer 27 are in ohmic contact. A cathode electrode film (not shown) is provided on the back surface of the n-type semiconductor substrate 21 opposite to the main surface 21a. The cathode electrode film and the n-type semiconductor substrate 21 are in ohmic contact.

  Subsequently, main steps in the method of manufacturing the semiconductor laser device according to the present embodiment will be described with reference to FIGS. 3 to 10 show side cross sections along the optical waveguide direction, and FIGS. 11 to 13 show cross sections orthogonal to the optical waveguide direction.

[First cladding layer forming step]
First, as shown in FIG. 3, an n-type cladding layer 52 is formed on an n-type semiconductor substrate 51 mainly including a III-V group compound semiconductor. The growth of the n-type cladding layer 52 is performed using, for example, a metal organic vapor phase growth furnace. As an example, the n-type semiconductor substrate 51 and the n-type cladding layer 52 are made of n-type InP.

[Laminated part forming step]
Next, a semiconductor stacked portion having an active layer is formed on the n-type cladding layer 52. First, as shown in FIG. 4, a first optical confinement layer 53 mainly including an n-type III-V compound semiconductor is grown on the n-type cladding layer 52. This growth is performed using, for example, a metal organic chemical vapor deposition furnace. As an example, the first optical confinement layer 53 is made of n-type AlGaInAs. The composition ratio of the n-type AlGaInAs is determined so that the PL wavelength is smaller than the PL wavelength of the active layer 54 (described later). As an example, when the PL wavelength of the active layer 54 is 1.3 [μm], the composition ratio is determined such that the PL wavelength of the n-type AlGaInAs is 1.1 [μm].

  Next, an active layer 54 is formed by growing a III-V group compound semiconductor containing Al in the composition on the first optical confinement layer 53 (active layer forming step). The active layer 54 includes a multiple quantum well structure and has a plurality of well layers and barrier layers that are alternately stacked. The well layer and the barrier layer are grown using, for example, a metal organic chemical vapor deposition reactor. As an example, the well layer and the barrier layer are made of undoped AlGaInAs. The composition ratio of the undoped AlGaInAs in the well layer is determined so that the PL wavelength exists in the vicinity of a predetermined wavelength to be output by the semiconductor laser element. As an example, the PL wavelength is determined to be 1.3 [μm].

  Thereafter, a second optical confinement layer 55 mainly including a p-type III-V compound semiconductor is grown on the active layer 54. This growth is performed using, for example, a metal organic chemical vapor deposition furnace. As an example, the second optical confinement layer 55 is made of p-type AlGaInAs. The composition ratio of the p-type AlGaInAs is determined in the same manner as the first optical confinement layer 53 described above.

  Subsequently, a diffraction grating layer is formed. First, as shown in FIG. 5, a lower semiconductor region 56 is formed by growing a III-V compound semiconductor on the active layer 54 (on the second optical confinement layer 55 in this embodiment). This III-V compound semiconductor preferably contains Al in the composition. As an example, the lower semiconductor region 56 is made of p-type AlInAs.

  Next, a plurality of light absorption regions are formed (light absorption region formation step). A semiconductor layer 57 is formed on the lower semiconductor region 56 by growing a group III-V compound semiconductor that does not substantially contain Al. As an example, the semiconductor layer 57 is made of semi-insulating GaInAsP doped with at least one of Ru and Fe. The composition ratio of GaInAsP is determined so as to absorb light having a wavelength emitted from the active layer 54, that is, the PL wavelength thereof substantially matches the PL wavelength of the active layer 54. As an example, when the PL wavelength of the active layer 54 is 1.3 [μm], the composition ratio is determined so that the PL wavelength of this GaInAsP is 1.3 [μm]. The lower semiconductor region 56 and the semiconductor layer 57 are grown using, for example, a metal organic vapor phase growth furnace.

Subsequently, a mask for forming a plurality of light absorption regions is formed on the semiconductor layer 57 as follows. First, an insulating film 58 made of a silicon-based inorganic compound film (for example, SiO ₂ ) is deposited on the semiconductor layer 57. This deposition is performed by, for example, chemical vapor deposition. Then, a resist 59 is applied on the silicon-based inorganic compound film. Thereafter, a plurality of periodically arranged patterns are transferred to the resist 59 to form a resist mask 60 shown in FIG. In this step, the resist mask 60 is formed so as to have a pattern corresponding to the plurality of light absorption regions 18 shown in FIGS. The resist mask 60 is formed using, for example, an electron beam exposure method or a lithography technique such as nanoimprint.

Subsequently, the insulating film 58 is etched using the resist mask 60. For this etching, for example, reactive ion etching using CF ₄ gas can be used. In this step, in order to secure a selection ratio between the resist mask 60 and the insulating film 58, it is preferable that the thickness of the insulating film 58 is set to about 20 [nm] in the previous step. When the resist mask 60 is removed by, for example, O ₂ ashing after the etching, a plurality of mask patterns 61 for forming a light absorption region are formed as shown in FIG. The arrangement period of the mask pattern 61 is set equal to the period Λ of the light absorption region 18 shown in FIG. That is, the arrangement period of the mask pattern 61 is set according to the wavelength of the laser beam to be output. For example, when the wavelength of the laser beam is 1550 [nm], it is set to 240 [nm]. Is 1300 [nm], it is set to 200 [nm].

Subsequently, the semiconductor layer 57 is etched using the mask pattern 61. In this example of etching, RIE using a CH ₄ / H ₂ mixed gas is used. In this step, etching is performed until the semiconductor layer 57 made of GaInAsP is penetrated. However, since there is a large difference in etching rate between GaInAsP and AlInAs, the lower semiconductor region 56 made of AlInAs is hardly etched. That is, the lower semiconductor region 56 functions as an etch stop layer for the semiconductor layer 57. By this step, a plurality of light absorption regions 62 are formed as shown in FIG. Thereafter, wet etching is performed to remove the damaged layer by RIE. For this wet etching, for example, a sulfuric acid-based etchant is used. Then, the mask pattern 61 is removed. For example, the mask pattern 61 made of silicon oxide is removed using buffered hydrofluoric acid.

  Subsequently, as shown in FIG. 9, an intermediate semiconductor region 63 is formed by embedding gaps between the plurality of light absorption regions 62 with a semiconductor having a lower refractive index than the light absorption region 62 (embedding step). In this embedding step, the intermediate semiconductor region 63 is formed by embedding gaps between the plurality of light absorption regions 62 with, for example, a group III-V compound semiconductor (for example, p-type AlInAs) having the same composition as the lower semiconductor region 56. It is good to form. This buried regrowth is performed using, for example, a metal organic vapor phase growth furnace. Thereafter, an III-V group compound semiconductor is further grown on the plurality of light absorption regions 62 and the intermediate semiconductor region 63 to form the upper semiconductor region 64. This III-V compound semiconductor preferably contains Al in the composition. As an example, the upper semiconductor region 64 is made of a III-V group compound semiconductor (in the example, p-type AlInAs) having the same composition as the intermediate semiconductor region 63, and in this case, the upper semiconductor region 64 is grown in the intermediate semiconductor region 63. Subsequent to burying regrowth can be performed continuously.

  Through the above steps, the carrier stop region 65 including the lower semiconductor region 56, the intermediate semiconductor region 63, and the upper semiconductor region 64 is formed. As a result, a diffraction grating layer 66 having a carrier stop region 65 and a plurality of light absorption regions 62 is formed, and a semiconductor including the first light confinement layer 53, the active layer 54, the second light confinement layer 55, and the diffraction grating layer 66. The stacked portion 67 is completed.

[Second clad layer forming step]
Subsequently, as shown in FIG. 10, a p-type cladding layer 68 and a p-type contact layer 69 are formed by growing a p-type III-V group compound semiconductor on the semiconductor stacked portion 67. The p-type cladding layer 68 and the p-type contact layer 69 are grown using, for example, a metal organic chemical vapor deposition furnace. As an example, the p-type cladding layer 68 is made of p-type InP, and the p-type contact layer 69 is made of high-concentration p-type GaInAs.

Subsequently, as shown in FIG. 11, the p-type cladding layer 68 and the p-type contact layer 69 are etched to form a striped ridge structure. As an example of the method, first, an insulating film such as SiO ₂ or SiN is deposited on the p-type contact layer 69 by chemical vapor deposition, and then a striped mask pattern is formed on the insulating film by a photolithography technique or the like. Then, the insulating film is etched using the mask pattern. Thereafter, dry etching using a CH ₄ / H ₂ mixed gas is performed on the p-type cladding layer 68 and the p-type contact layer 69 using the insulating film as an etching mask, whereby the ridge structure shown in FIG. 11 can be formed.

  Then, wet etching is performed using a solution of hydrochloric acid and acetic acid in order to remove a damaged layer caused by dry etching. At this time, the p-type cladding layer 68 made of InP is preferably etched, but even if the upper semiconductor region 64 is exposed after passing through the p-type cladding layer 68 by etching, the upper semiconductor region 64 made of AlInAs is almost etched. Not. That is, the upper semiconductor region 64 functions as an etch stop layer when the p-type cladding layer 68 is etched. By this step, the upper semiconductor region 64 is exposed as shown in FIG. 12, and a portion (ridge portion 68a) corresponding to the ridge portion 13a shown in FIG. 1 is formed.

Thereafter, as shown in FIG. 13, an insulating film 70 made of SiO ₂ is deposited so as to cover the surface of the p-type contact layer 69, the side surface of the ridge portion 68a, the exposed surface of the upper semiconductor region 64, and the like. After the resin 71 is applied and planarized, openings are formed in the BCB resin 71 and the insulating film 70 located above the ridge portion 68a. Then, the anode electrode film 72 in contact with the p-type contact layer 69 is vapor-deposited through the opening, and the cathode electrode film 73 is vapor-deposited on the back surface of the semiconductor substrate 51, thereby completing the semiconductor laser device according to the present embodiment.

  The operational effects obtained by the semiconductor laser device 10 according to the present embodiment and the manufacturing method thereof will be described. When the active layer contains Al in the composition as in the semiconductor laser device 10 of this embodiment, it is not preferable to etch the active layer. This is because when the active layer is etched, the active layer is oxidized and affects the laser characteristics. Further, the active layer may be damaged by microfabrication when forming the diffraction grating, non-radiative recombination may increase, and laser characteristics may deteriorate.

  In the semiconductor laser device 10 and the manufacturing method thereof according to the present embodiment, the plurality of light absorption regions 18 (62) that absorb the light having the wavelength emitted by the active layer 15 has a period corresponding to the predetermined wavelength to be output at the active layer 15. (54). Thereby, the light absorption characteristic in the optical waveguide direction periodically changes. As a result, the gain also changes periodically, and a gain-coupled DFB laser device can be suitably realized. And when forming such a light absorption area | region 18 (62), the process of the active layer 15 (54) is not required. Therefore, according to the semiconductor laser device 10 and the manufacturing method thereof of the present embodiment, a gain coupled DFB structure can be easily obtained without processing the active layer 15 (54). Further, in order to obtain a stable single mode characteristic in the refractive index coupled DFB laser, it is necessary to provide a phase shift, but in the semiconductor laser device 10 of the present embodiment, such a phase shift is unnecessary.

  In the semiconductor laser device 10 and the manufacturing method thereof, the intermediate semiconductor region 19b (63) having a lower refractive index than the plurality of light absorption regions 18 (62) is provided between the plurality of light absorption regions 18 (62). . Thereby, a periodic refractive index distribution can be formed in the direction along the active layer 15 (54). Therefore, a refractive index coupling component and a gain coupling component are generated in the light guiding direction, and a more stable single mode operation and low threshold current operation can be realized by their synergistic effect (complex coupling). In particular, if the light absorption region 18 (62) is formed of GaInAsP and the intermediate semiconductor region 19b (63) is formed of AlInAs as in the present embodiment, more effective refractive index coupling due to a large refractive index difference between the two. The effect can be obtained.

  Further, when a ridge waveguide type semiconductor laser device is manufactured as in the present embodiment, the p-type cladding layer 68 is etched until the semiconductor stacked portion 67 is exposed, thereby forming a stripe-shaped ridge structure (ridge portion). 68a) may be formed. In such a case, an upper semiconductor region 64 containing Al in the composition is grown on the plurality of light absorption regions 62 and the intermediate semiconductor region 63, and a p-type cladding layer 68 is formed thereon, thereby including Al. The upper semiconductor region 64 functions as an etch stop layer when the p-type cladding layer 68 is etched (particularly, wet etching using a hydrochloric acid and acetic acid solution for removing a damaged layer). Therefore, a striped ridge structure can be easily formed in the p-type cladding layer 68.

  Further, as in the present embodiment, in the stacked portion forming step, the III-V group compound semiconductor (lower semiconductor region 56) containing Al in the composition is activated between the active layer forming step and the light absorption region forming step. A step of growing on the layer 54 may be included. Thereby, the lower semiconductor region 56 functions as an etch stop layer when the plurality of light absorption regions 62 are formed. Therefore, it is possible to prevent the etching from reaching the active layer 54 when the light absorption region 62 is formed.

  The semiconductor laser device and the manufacturing method thereof according to the present invention are not limited to the above-described embodiments, and various other modifications are possible. For example, in the above embodiment, AlGaInAs is used as the composition of the active layer containing Al in the composition, GaInAsP is used as the composition of the light absorption region substantially not containing Al, and the lower and upper semiconductor regions containing Al in the composition are used. Although AlInAs is illustrated as the composition, the composition of each layer is not limited to these, and various compositions can be applied as long as they are III-V group compound semiconductors containing (or not containing) Al.

FIG. 1 is a perspective sectional view showing the structure of a semiconductor laser device according to an embodiment of the present invention. FIG. 2 is a side cross-sectional view showing the II-II cross section of FIG. It is a figure explaining the 1st clad layer formation process in the method of producing a semiconductor laser element. It is a figure explaining the active layer formation process among the lamination part formation processes in the method of producing a semiconductor laser element. It is a figure explaining the light absorption area | region formation process among the lamination | stacking part formation processes in the method of producing a semiconductor laser element. It is a figure explaining the light absorption area | region formation process among the lamination | stacking part formation processes in the method of producing a semiconductor laser element. It is a figure explaining the light absorption area | region formation process among the lamination | stacking part formation processes in the method of producing a semiconductor laser element. It is a figure explaining the light absorption area | region formation process among the lamination | stacking part formation processes in the method of producing a semiconductor laser element. It is a figure explaining the embedding process among the lamination part formation processes in the method of manufacturing a semiconductor laser element. It is a figure explaining the 2nd clad layer formation process in the method of manufacturing a semiconductor laser element. It is a figure explaining the 2nd clad layer formation process in the method of manufacturing a semiconductor laser element. It is a figure explaining the 2nd clad layer formation process in the method of manufacturing a semiconductor laser element. It is a figure explaining the other process in the method of manufacturing a semiconductor laser element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Semiconductor laser element 11, 52 ... N-type clad layer, 12, 67 ... Semiconductor laminated part, 13, 68 ... P-type clad layer, 13a, 68a ... Ridge part, 14, 53 ... First optical confinement layer, 15 , 54 ... Active layer, 16, 55 ... Second optical confinement layer, 17, 66 ... Diffraction grating layer, 18, 62 ... Light absorption region, 19, 65 ... Carrier stop region, 19a, 56 ... Lower semiconductor region, 19b, 63 ... Intermediate semiconductor region, 19c, 64 ... upper semiconductor region, 21,51 ... n-type semiconductor substrate, 24 ... buried region, 25, 58,70 ... insulating film, 27,69 ... p-type contact layer, 57 ... semiconductor Layer 59, resist, 60 ... resist mask, 61 ... mask pattern, 71 ... BCB resin, 72 ... anode electrode film, 73 ... cathode electrode film.

Claims (6)

A semiconductor laser element that outputs laser light of a predetermined wavelength,
A first conductivity type semiconductor substrate containing a III-V compound semiconductor;
A first conductivity type cladding layer provided on the semiconductor substrate;
A semiconductor laminate having an active layer and provided on the first conductivity type cladding layer;
A second conductivity type cladding layer provided on the semiconductor laminate,
The semiconductor stacked portion further includes a plurality of light absorption regions arranged along the active layer at a period corresponding to the predetermined wavelength and absorbing light having a wavelength emitted from the active layer,
The active layer is made of a III-V group compound semiconductor containing Al in the composition,
The semiconductor laser device, wherein the plurality of light absorption regions are made of a III-V group compound semiconductor substantially not containing Al.   The semiconductor laser device according to claim 1, further comprising an intermediate semiconductor region having a lower refractive index than the plurality of light absorption regions between the plurality of light absorption regions. A method for producing a semiconductor laser element that outputs laser light of a predetermined wavelength,
A first cladding layer forming step of forming a first conductivity type cladding layer on a first conductivity type semiconductor substrate containing a III-V group compound semiconductor;
A laminated portion forming step of forming a semiconductor laminated portion having an active layer on the first conductivity type cladding layer;
A second clad layer forming step of forming a second conductivity type clad layer on the semiconductor laminated portion,
The laminated part forming step includes
An active layer forming step of growing a group III-V compound semiconductor containing Al in the composition to form the active layer;
A plurality of mask patterns arranged on the group III-V compound semiconductor after growing a group III-V compound semiconductor that absorbs light having a wavelength emitted from the active layer and does not substantially contain Al A light absorption region forming step of forming a plurality of light absorption regions arranged along the active layer at a period corresponding to the predetermined wavelength by etching the III-V compound semiconductor using a mask having A method for manufacturing a semiconductor laser device, comprising:   4. The semiconductor according to claim 3, wherein the stacked portion forming step further includes a filling step of filling a gap between the plurality of light absorption regions with a semiconductor having a lower refractive index than the plurality of light absorption regions. A method for manufacturing a laser element. The laminated part forming step includes
An embedding step of filling a gap between the plurality of light absorption regions with a semiconductor;
The method further comprises: growing a group III-V compound semiconductor containing Al in the composition on the plurality of light absorption regions and on the semiconductor buried in the embedding step. A manufacturing method of the semiconductor laser device described in 1.   The laminated portion forming step further includes a step of growing a III-V group compound semiconductor containing Al in the composition on the active layer between the active layer forming step and the light absorption region forming step. The method for manufacturing a semiconductor laser device according to claim 3, wherein the method is characterized in that:

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