JPH1187856A - Gallium nitride compound semiconductor laser and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride compound semiconductor laser which is capable of oscillating continuously and stably in a basic lateral mode, of low astigmatism, and low in threshold current density by a method wherein a light trapping layer whose refractive index is larger than that of a current injection part is provided to a current block layer, and furthermore the current injection part has a structure where it becomes gradually large in refractive index starting from its center toward ends. SOLUTION: The gallium nitride compound semiconductor laser of this invention has a structure where a quantum well structure active layer 107 whose refractive index is set larger at its periphery than at the center of its stripe, a P-GaN waveguide layer 108, and a P-AlGaN clad layer 109 are successively formed above an N-Al0.15 Ga0.85 N clad layer 103 and an N-GaN waveguide layer 104, a P-In0.1 Ga0.9 N current block layer 105 and an N-In0.1 Ga0.9 N current block layer 106 both large in refractive index are each formed on both the sides of the stripe, and furthermore a P-Al0.15 Ga0.85 N clad layer 110 is formed on all the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a nitride compound semiconductor material, and more particularly to InGaAs.
The present invention relates to a semiconductor laser made of an lBN-based material and a method for manufacturing the same.

[0002]

2. Description of the Related Art A semiconductor laser using an InGaAlN material has been developed as a short wavelength light source required for high density optical discs. A laser using a multiple quantum well structure has been reported as a structure that achieves oscillation by current injection in this material system.

It is known that a multiple quantum well structure using a thin film active layer for a bulk active layer can greatly reduce the threshold. However, in this material system, since the threshold current density is still high and the operating voltage is high, there are many problems to realize continuous oscillation.

One of the causes of a high operating voltage in an InGaAlN-based laser is that the p-type contact resistance is extremely large. In the electrode stripe structure already reported,
The voltage drop in the p-type electrode stripe is large, the operating voltage is increased, and the generation of heat in this region cannot be ignored. To reduce the contact resistance, it is sufficient to increase the electrode area. However, in the above-mentioned electrode stripe structure, the threshold current value increases when the electrode area is increased, and the fundamental transverse mode oscillation does not occur because the current injection region is large. It is possible.

In applications to optical disks and the like, it is necessary to focus the emitted beam to a minimum spot, so that fundamental transverse mode oscillation is indispensable. However, a transverse mode control structure has not been realized with an InGaAlN-based laser. In a conventional material system, for example, a ridge stripe type SB of InGaAlP system is used.
R lasers have been reported.

However, this structure cannot be applied to an InGaAlN-based laser as it is because the material system is different from this. As a current confinement structure in the InGaAlN system, Japanese Patent Application Laid-Open No. HEI 8-111558 discloses a structure using GaN as a current confinement layer. This structure allows current confinement, but does not have a light confinement effect, so that it is difficult to obtain a high-quality output beam free of astigmatism and the like.

In general, in order for a current confinement layer provided in a cladding layer to also function as a light confinement layer, its composition, thickness, distance from the active layer, and the like must be set to predetermined values. Particularly, in the case of an InGaAlN-based laser, since the oscillation wavelength is short, even if the composition is the same, a completely different waveguide mechanism is obtained depending on the thickness and position. Therefore, stable fundamental transverse mode oscillation cannot be obtained simply by providing the current confinement layer.

On the other hand, various specifications are required for a semiconductor laser used in an optical disk system. In particular, the write-once type and rewritable type require a low-output semiconductor laser for reproduction and reading and a high-output semiconductor laser for erasing and recording, and have different specifications. A high-power semiconductor laser generally uses a thin-film active layer structure, but this structure is not necessarily suitable for a reading laser. The readout laser is required to have low noise characteristics. For this purpose, for example, a self-pulsation type structure is used. However, it is difficult to obtain self-pulsation with an ultra-thin active layer structure. Therefore, a high-frequency superposition method, a method using two types of lasers, and the like have been adopted, but both have complicated structures. A method of forming two types of lasers by changing the thickness of the active layer depending on the location has also been reported, but there is a problem that it is difficult to control the thickness of the active layer.

Furthermore, as the density of optical discs increases, semiconductor lasers having different wavelengths will be used. However, compatibility with conventional optical disc systems is required. It may be. This is particularly necessary when the wavelength difference is large, such as red and blue. This is because the pit depth of the optical disk is optimized at the wavelength used, and if the reproduction wavelength is significantly different, the SN of the signal due to reflection from the pits will be reduced.

[0010]

As described above, the conventional In
It is difficult to fabricate a lateral mode control structure with a GaAlN-based semiconductor laser, and it has been difficult to realize a semiconductor laser that continuously oscillates in a fundamental transverse mode. Further, it has been difficult to realize the laser performance required for both reproduction / read and erasure / recording in an optical disk system. Furthermore, it has been difficult to realize a semiconductor laser that can be used for both optical disc systems having different wavelengths and different recording densities, which is necessary for ensuring compatibility.

The present invention has been made in consideration of the above circumstances, and has as its object to be able to continuously oscillate in a stable fundamental transverse mode, and to provide astigmatism suitable for a light source such as an optical disk system. An object of the present invention is to provide an InGaAlN-based semiconductor laser capable of obtaining a high-quality emission beam. It is another object of the present invention to provide a semiconductor laser capable of realizing laser performance required for both reproduction / read and erasure / recording in an optical disk system without requiring a difficult process, and a method of manufacturing the same. It is in.

Still another object of the present invention is to provide a semiconductor laser which is necessary for ensuring compatibility between optical disk systems having different design wavelengths and can be used for both, and a method of manufacturing the same.

[0013]

The gist of the present invention is to provide a light confinement layer having a large refractive index and to control a transverse mode by a loss guiding effect or an anti-guiding effect.
An object of the present invention is to enable continuous oscillation in a basic transverse mode in which the operating voltage is low and stable.

[0014] The present invention provides a gallium nitride compound semiconductor _{(Ga x In y Al z B} 1-xyz N: 0 ≦ x, y,
z, x + y + z ≦ 1), in a semiconductor laser having an active layer sandwiched between semiconductor layers of different conductivity types, a stripe-shaped current injection portion for injecting carriers into the active layer is formed. At least one or more current blocking layers are formed on both sides of the substrate, and the current injection portions are configured to have different equivalent refractive indices.

Here, preferred embodiments of the present invention include the following. (1) The current injection portion has a structure in which the equivalent refractive index in the direction perpendicular to the stripe and the current injection direction is larger at the end of the injection constriction portion than at the center of the current injection portion, and the current blocking layer is formed of the current injection portion. A gallium nitride-based compound semiconductor material having a refractive index equivalently higher than the ends. (2) The current injection portion has a structure in which the equivalent refractive index in the direction perpendicular to the stripe and the current injection direction is larger at the end of the injection constriction portion than at the center of the current injection portion, and the current blocking layer is formed of the current injection portion. It should be made of a nitride-based compound semiconductor material having a large absorption loss and a large refractive index because the bandgap energy is smaller than the center. (3) the current blocking layer is made of gallium nitride-based compound semiconductor material, the active layer portion is at least In _a Ga _b Al _{c
B 1-abc N (0 ≦} a, b, c, a + b + c ≦ 1) consisting of a well layer and the _{In e Ga f Al g B 1} -efg N (0 ≦
e, f, g, e + f + g ≦ 1) and a barrier layer composed of a single quantum well or multiple quantum wells.

Further, the present invention is characterized in that a semiconductor laser for generating a plurality of laser beams is provided with a plurality of active layer structures having different active layer compositions or thicknesses or widths.

[0017] The present invention is a gallium nitride compound semiconductor _{(Ga x In y Al z B} 1-xyz N: 0 ≦ x, y,
z, x + y + z ≦ 1), in a method of manufacturing a gallium nitride-based compound semiconductor laser in which an active layer is sandwiched between semiconductor layers of different conductivity types, a step of forming at least one or more current blocking layers. A step of selectively removing the current block layer; and a step of forming a layer structure to be a current injection portion by selectively growing crystals in a portion removed by the step. Another one
One method is a gallium nitride-based compound semiconductor (Ga _x In
_{y Al z B 1-xy- z} N: 0 ≦ x, y, z, x + y + z ≦
(1) a step of selectively growing a layer structure serving as a current injection part when manufacturing a gallium nitride compound semiconductor laser in which an active layer is sandwiched between semiconductor layers of different conductivity types;
A step of forming at least one current blocking layer on both sides of the current injection portion may be employed.

Here, as a preferred embodiment of the present invention, a gallium nitride-based compound semiconductor (Ga _h In _i Al) of the same conductivity type as the surface of the current injection portion is provided on the block layer and the current injection portion. _j B _1-hIj N: 0 ≦ h,
i, j, h + i + j ≦ 1).

According to the present invention, in the InGaAlBN-based semiconductor laser, the current blocking layer is provided with a light confinement layer having a larger refractive index than the current injection part, and the current injection part increases the refractive index from the center to the end. As a result, the higher-order mode is suppressed, the continuous oscillation in the stable fundamental transverse mode becomes possible, and the threshold current density can be reduced.

Further, according to the present invention, a low-power, low-noise laser having a thick film active layer and a high-power laser having a thin film active layer can be formed on the same substrate. It is possible to achieve the laser performance required for both reproduction / readout and erasure / recording. Furthermore, according to the present invention, lasers having different wavelengths can be formed on the same substrate, so that the problem of incompatibility due to a difference in wavelength can be solved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 is for explaining a schematic configuration of a gallium nitride-based blue semiconductor laser device according to a first embodiment of the present invention. In the figure, 101 is a sapphire substrate, 102 is an n-GaN contact layer (Si-doped,
5 + 10 ¹⁸ cm ⁻³ , 4 μm), 103 is n-Al _0.15 Ga
_0.85 N cladding layer (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.
3), 104 is an n-GaN waveguide layer (Si-doped,
0.1 μm), 105 is p-In _0.1 Ga _0.9 N (Mg
Doping, 1 × 10 ¹⁸ cm ⁻³ , 0.2 μm) current blocking layer, 106 is n-In _0.1 Ga _0.9 N (Si-doped, 1
× 10 ¹⁸ cm ⁻³ , 0.1 μm) current blocking layer, 107 is an InGaN quantum well (undoped, the center of the groove is In
_0.2 Ga _0.8 N, 2 nm) and 10 layers of InG
aN barrier layer (undoped, the center of the groove is In _0.05 Ga
_0.95 N, 4 nm) quantum well structure (SCH-MQ
W; Separete Confinement Heterostructure Multi-Qua
ntum Well) active layer 108 is a p-GaN waveguide layer (Mg)
Dope, the center of the groove is 0.1 μm), 109 is p-Al
GaN clad layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ , center of groove is Al _0.20 Ga _0.80 N, 0.1 μm), 110 is p-Al _0.15 Ga _0.85 N clad layer (Mg doped, 1 ×
10 ¹⁸ cm ⁻³ , 0.3 μm), 111 is a p-GaN contact layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ , 1 μm), 11
2 is Pt (10 nm) / Ti (20 nm) / Pt (30
nm) / Au (1 μm) structure p-side electrode, 113 is Al /
The Ti / Au structure n-side electrode 114 is a SiO ₂ insulating film. Although not particularly shown, a high reflection coating in which TiO ₂ / SiO ₂ is laminated in multiple layers is applied to the laser light emitting end face.

Next, a method of manufacturing the above-mentioned nitride compound semiconductor laser will be described with reference to the cross-sectional views in FIG. First, as shown in FIG. 7A, an n-GaN contact layer 102 is used to form n-InGaN on a sapphire substrate by metal organic chemical vapor deposition (hereinafter abbreviated as MOCVD).
The current block layer 106 is grown, a SiO ₂ mask is deposited, a part of the SiO ₂ mask is removed in a stripe shape with a width of 7 μm, and n-GaN is dry-etched using the SiO ₂ as an etching mask and containing chlorine gas. A groove up to the waveguide layer 104 is formed. Next, as shown in FIG. 7B, the layers from the SCH-MQW active layer 107 to the p-AlGaN cladding layer 109 are selectively grown as an SiO ₂ mask. Here, since no crystal grows on the SiO ₂ mask, selective growth can be performed only in a region where SiO ₂ is removed in a stripe shape. Moreover, SiO
₂ is 1/20 compared to the width of the SiO ₂ mask
In the following cases, the crystal growth rate increases as the distance from the center of the stripe to SiO ₂ increases, and as a result, the film thickness increases from the center to the periphery. In particular, SCH-M
InGaN constituting the QW active layer 107 also has a higher refractive index in a gradient manner since the In composition becomes higher from the center toward the periphery. In the case of the first embodiment of the present invention, SCH-M
In the QW active layer 107, the InGaN quantum well layer has In _0.2 Ga _0.8 N and a thickness of 2 nm at the center of the stripe, In _0.25 Ga _0.75 N and a thickness of 3 nm at the periphery of the stripe, and the InGaN barrier layer has a center of the stripe. In the portion, In _0.05 Ga _0.95 N and a thickness of 4 nm were formed, and in the periphery of the stripe, In _0.09 Ga _0.91 N and a thickness of 5.5 nm were formed. Next, as shown in FIG. 7C, the SiO ₂ mask is removed, and the p-AlGaN cladding layer 110 and the p-Ga
The N contact layer 111 is grown. Next, as shown in FIG. 7D, a stripe-shaped mesa is formed, and an SiO ₂ insulating film 114 is deposited on the entire surface of the wafer to a thickness of 900 nm.
-Pt / Ti / Pt on top of GaN contact layer 111
An Al / Ti / Au structure n-side electrode 113 is formed on a part of the n-GaN contact layer 102. Next, the back surface of the sapphire substrate 101 was mirror-polished to a thickness of 50 μm, and further cleaved along a plane perpendicular to the current confinement structure. On the cleavage plane, TiO ₂ / SiO _{2 (} not shown) was laminated in multiple layers. As shown in FIG. 6, a heat sink 1 having high thermal conductivity such as Cu, cubic boron nitride, or diamond is applied.
15 on which metallized Ti / Pt / Au etc.
Then, thermocompression bonding using AuSn eutectic solder 117 is performed. Here, if the p-side electrode 112 directly above the SCH-MQW active layer 107 is thermocompression-bonded to the heat sink 115, there is no problem in heat dissipation. Further, the Ti / Pt / Au metallized layer 1 is formed using an Au wire or an Al wire for current injection.
16 is wired. The order of the manufacturing process is not limited to the configuration shown in FIG. In order to make the refractive index distribution of the current injection portion as in the present invention, n-type is deposited on the sapphire substrate by MOCVD.
GaN contact layer 102 to n-GaN waveguide layer 104
And a SiO ₂ mask is deposited. A part of the SiO ₂ mask is removed in a stripe shape with a width of 7 μm.
From the MQW active layer 107 to the p-AlGaN cladding layer 10
9 and a p-AlGaN cladding layer 10
9 is covered with a SiO ₂ mask, and the p-InGaN current blocking layer 105 to the n-InGaN current blocking layer 10 are covered.
Even when 6 is formed, a current injection portion having a different refractive index in the lateral direction can be formed in the selective growth step by the MOCVD method.

In this embodiment, when the resonator length was 0.5 mm, the threshold current was 70 mA, the oscillation wavelength was 420 nm, the operating voltage was 5.2 V, and continuous oscillation was performed at room temperature. Further 50 ° C, 5m
The element life in W driving was 5000 hours or more.
The astigmatic difference was as small as 5 μm, and beam characteristics suitable for optical disc applications were obtained. In the case of this laser, p-Al
_0.15 Ga _0.85 N cladding layer 110 and n-Al _0.15 Ga
The equivalent refractive index of the active region where the current is injected from the SCH-MQW active layer 107 sandwiched by the _0.85 N cladding layer 103 to the p-AlGaN cladding layer 109 is p-In _0.1 Ga.
_0.9 N current blocking layer 105 to n-In _0.1 Ga _0.9
It is formed from an anti-waveguide structure that is lower than the non-conducting region up to the N current block layer 106. In addition, the stripe-shaped current injection portion has a stripe because the equivalent refractive index increases in a region near the current block layer. Even if the width is not reduced, the effect of the anti-guide structure increases, and the condition that the primary mode of the horizontal transverse mode is cut off, that is, only the fundamental transverse mode is likely to exist, so that the astigmatic difference is reduced. Further, it is clear from experiments by the inventors that InGaN has the largest gain when the well layer width compatibility is 2 nm, and that the InGaN quantum well layer of the SNH-MQW active layer 107 has a central part of a stripe having a thickness of 2 nm. The difference between the gain and the peripheral portion of the stripe having a thickness of 3 nm is increased, so that the controllability of the waveguide mode is improved.

The p-InGaN current blocking layer 10
When the In composition of the 5 and n-InGaN current blocking layers 106 is higher than the InGaN quantum well layer of the SCH-MQW active layer 107, the current blocking layers 105 and 106 have large absorption loss with respect to the oscillation wavelength, and the waveguide mode Of the current blocking layers 105 and 106 becomes lower than that of the current injection part, but this case is also very effective in stabilizing the fundamental transverse mode.
This is because the current block layer is a loss region, so that the higher-order mode in which seepage is large has a larger loss or cutoff as compared with the fundamental mode, but the threshold current density is slightly smaller than that in the anti-guided structure. Become higher.

FIG. 2 is a view for explaining a schematic configuration of a gallium nitride-based blue semiconductor laser device according to a second embodiment of the present invention. In the figure, 201 is a sapphire substrate, 2
02 is an n-GaN contact layer (S-doped, 5 × 10 ¹⁸
cm ⁻³ , 4 μm), 203 is an n-Al _0.15 Ga _0.85 N cladding layer (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.3 μm),
Reference numeral 204 denotes an n-GaN waveguide layer (Si-doped, 0.1 μm).
m) and 205 are p-In _0.1 Ga _0.9 N (Mg-doped,
1 × 10 ¹⁸ cm ⁻³ , 0.2 μm) Current blocking layer, 206
Is n-In _0.1 Ga _0.9 N (Si-doped, 1 × 10 ¹⁸ cm
^-3 , 0.1 μm) current blocking layer, 207 is InGaN
Quantum well (undoped, the center of the groove is In _0.2 Ga _0.8
N, 2 nm) and an InGaN barrier layer sandwiching it (undoped, the center of the groove is In _0.05 Ga _0.95 N, 4n
m) a quantum well structure (SCH-MQW) active layer comprising:
208 is a p-GaN waveguide layer (Mg doped, the center of the groove is 0.1 μm), 209 is a p-AlGaN cladding layer (M
g-doped, 1 × 10 ¹⁸ cm ⁻³ , center of groove is Al _0.20 Ga
_0.80 N, 20 nm), 210 is p-In _0.25 Ga _0.75 N
Layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ , 50 nm), 211
_{Represents a} p-Al _0.15 Ga _0.85 N cladding layer (Mg doped, 1
× 10 ¹⁸ cm ⁻³ , 0.3 μm), 212 is a p-GaN contact layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ , 1 μm), 2
13 is Pt (10 nm) / Ti (20 nm) / Pt (3
0 nm) / Au (1 μm) structure p-side electrode, 214 is Al
The / Ti / Au structure n-side electrode 215 is a SiO ₂ insulating film. Although not particularly shown, a high reflection coating in which TiO ₂ / SiO ₂ is laminated in multiple layers is applied to the laser light emitting end face.

This embodiment is different from the first embodiment of the present invention shown in FIG. 1 in that the p-In _0.25 Ga _0.75 N layer 2
11 is inserted. In the case of this laser, in the manufacturing process, the p-AlGaN cladding layer 209 and the n-In _0.1 Ga _0.9 N current blocking layer 2 exposed to the air are used.
06 on each surface from a relatively low temperature to p-In _0.25 Ga
Since the growth of the _0.75 N layer 211 can be started, p-AlGaN
In addition to preventing the evaporation of constituent elements from the surfaces of the cladding layer 209 and the n-In _0.1 Ga _0.9 N current blocking layer 206, the p-In _0.25 Ga _0.75 N layer 211 functions as a saturable absorption layer, so that the beam characteristics are reduced. Is improved.

FIG. 3 is a view for explaining a schematic configuration of a gallium nitride-based blue semiconductor laser device according to a third embodiment of the present invention. In the figure, 301 is a sapphire substrate, 3
02 is an n-GaN contact layer (Si-doped, 5 × 10
¹⁸ cm ⁻³ , 4 μm), 303 is an n-Al _0.15 Ga _0.85 N cladding layer (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.3 μm)
m) and 304 are n-GaN waveguide layers (Si-doped, 0.1
μm) and 305 are 10 layers of In _0.2 Ga _0.8 N quantum wells (undoped, 2 nm) and In _0.05 Ga _0.95 sandwiching them.
Quantum well structure (SCH-MQW) active layer composed of an N barrier layer (undoped, 4 nm), 306 is a p-GaN waveguide layer (Mg doped, 0.1 μm), 307 is n-In _0.1 G
a _0.9 N (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.2 μm)
The current block layer 308 is n-Al _0.15 Ga _0.85 N (S
i-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.1 μm), current blocking layer, 309 is a p-In _0.25 Ga _0.75 N layer (Mg-doped, 1 × 10 ¹⁸ cm ⁻³ , 50 nm), 310 is Al _0.20 G
a _0.80 N cladding layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ ,
0.111 μm) and 311 are p-Al _0.15 Ga _0.85 N cladding layers (Mg doped, 1 × 10 ¹⁸ cm ⁻³ , 0.3 μm), 311
12 is a p-GaN contact layer (Mg doped, 1 × 10
¹⁸ cm ⁻³ , 1 μm), 313 is Pt (10 nm) / Ti
(20 nm) / Pt (30 nm) / Au (μm) structure p
Side electrode 314 is an Al / Ti / Au structure n-side electrode, 31
Reference numeral 5 denotes a SiO ₂ insulating film. Although not particularly shown, a high reflection coating in which TiO ₂ / SiO ₂ is laminated in multiple layers is applied to the laser light emitting end face.

In the case of the laser of this embodiment, p-Al _0.15 G
a-In _0.25 Ga _0.75 N layer 309 sandwiched between a _0.85 N cladding layer 311 and p-GaN waveguide layer 306 and Al _0.20 G
a _0.80 N-cladding layer 310 has a p-I
n _0.1 Ga _0.9 N current blocking layer 307 and n-Al _0.15
The anti-waveguide structure is formed with a lower equivalent refractive index than the current block layer composed of the Ga _0.85 N current block layer 308, and the central part of the current injection part has a lower refractive index than the peripheral part. Therefore, as in the first embodiment of the present invention, the horizontal / lateral mode is only the basic mode, and the astigmatic difference is reduced.

FIG. 4 is a view for explaining a schematic configuration of a gallium nitride-based blue semiconductor laser device according to a fourth embodiment of the present invention. In the figure, 401 is a sapphire substrate, 4
02 is an n-GaN contact layer (Si-doped, 5 × 10
¹⁸ cm ⁻³ , 4 μm) and 403 are n-Al _0.15 Ga _0.85 N cladding layers (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.3 μm)
m) and 404 are n-GaN waveguide layers (Si-doped, 0.1
μm), 405 is a layer of 10 layers of In _0.2 Ga _0.8 N quantum wells (undoped, 2 nm) and In _0.05 Ga _0.95 sandwiching them.
Quantum well structure (SCH-MQW) active layer composed of an N barrier layer (undoped, 4 nm), 406 is a p-GaN waveguide layer (Mg doped, 0.1 μm), 407 is n-In _0.1 G
a _0.9 N (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.2 μm
m), current block layer, 408 is n-Al _0.15 Ga _0.85
N (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.1 μm) current blocking layer, 409 is a p-In _0.25 Ga _0.75 N layer (Mg-doped, 1 × 10 ¹⁸ cm ⁻³ , 50 nm), 410 is Al _0.20
Ga _0.80 N cladding layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ ,
0.1 μm) and 411 are p-In _0.25 Ga _0.75 N layers (M
g-doped, 1 × 10 ¹⁸ cm ⁻³ , 50 nm), 412 is p-
Al _0.15 Ga _0.85 N cladding layer (Mg doped, 1 × 10
¹⁸ cm ^{-3, 0.3μm),} 413 is the p-GaN contact layer (Mg ^{doped, 1 × 10 18 cm -3,} 1μm), 414 is Pt (10nm) / Ti (20nm ) / Pt (30n
m) / Au (1 μm) structure p-side electrode, 415 is Al / T
An i / Au structure n-side electrode 416 is a SiO ₂ insulating film. Although not particularly shown, a high reflection coating in which TiO ₂ / SiO ₂ is laminated in multiple layers is applied to the laser light emitting end face.

This embodiment differs from the third embodiment of the present invention shown in FIG. 3 in that the second embodiment of the present invention differs from the first embodiment of the present invention in that p -In _0.25 G
a _0.75 N layer 411 was inserted. Therefore, similarly to the second embodiment of the present invention, the burying growth can be performed from a low temperature, so that deterioration of the underlying layer can be prevented.

FIG. 5 is a view for explaining a schematic configuration of a gallium nitride-based blue semiconductor laser device according to a fifth embodiment of the present invention. In the figure, 501 is a sapphire substrate, 5
02 is an n-GaN contact layer (Si-doped, 5 × 10
¹⁸ cm ⁻³ , 4 μm) and 503 are n-Al _0.15 Ga _0.85 N cladding layers (Si-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.3 μm)
m) and 504 are n-GaN waveguide layers (Si-doped, 0.1
μm), 505 is a p-In _0.1 Ga _0.9 N (Mg-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.2 μm) current blocking layer,
06 is n-In _0.1 Ga _0.9 N (Si-doped, 1 × 10
¹⁸ cm ^-3 , 0.1 μm) current blocking layer, 507 A and 5
07B is an InGaN quantum well (undoped, the center of the groove is In _0.3 Ga _0.7 N, 4 nm and In _0.2 Ga _{0.8, respectively).}
N, 2 nm) and an InGaN barrier layer sandwiching them (undoped, the center of the groove is In _0.1 Ga _0.9 N, respectively).
A quantum well structure (SCH-MQW) active layer composed of 8 nm and In _0.05 Ga _0.95 N, 4 nm), 508A and 508
B is a p-GaN waveguide layer (Mg doped, the center of the groove is 0.1 μm and 0.06 μm, respectively), and 509A and 509B are p-AlGaN cladding layers (Mg doped, 1 × 10 ¹⁸ cm)
^-3 , the center of the groove is Al _0.20 Ga _0.80 N, and the film thickness is _{0.1 mm} .
1 μm and 0.06 μm), and 510 is p-Al _0.15 Ga
_0.85 N cladding layer (Mg-doped, 1 × 10 ¹⁸ cm ⁻³ , 0.
511 is a p-GaN contact layer (Mg doped, 1 × 10 ¹⁸ cm ⁻³ , 1 μm) and 512 is Pt (10n
m) / Ti (20 nm) / Pt (30 nm) / Au (1
μm) Structure p-side electrode, 513: Al / Ti / Au structure n
The side electrodes 514 are SiO ₂ insulating films. Although not particularly shown, TiO ₂ / Si
A high reflection coat in which O ₂ is laminated in multiple layers is applied.

This embodiment differs from the first embodiment of the present invention shown in FIG. 1 in that the width of the current injection portion is 5 μm and 1 μm.
0 μm. SCH-MQW active layers 507A and 507 by selective growth using SiO ₂ mask
In the formation of 07B, as the stripe width becomes smaller, the composition of the InGaN quantum well layer that determines the laser oscillation wavelength becomes higher and the film thickness becomes thicker. Therefore, an In _0.3 Ga _0.7 N, 4 nm quantum well layer is formed at the center of the current injection portion A having a stripe width of 5 μm, and In _0.2 Ga _0.8 N, 2 nm quantum well layer is formed at the center of the current injection portion B having a stripe width of 10 μm. A layer was formed and oscillated at a wavelength of 425 nm and a wavelength of 420 nm, respectively. In the case of this laser, the current injection section A operates as a low-power, low-noise laser of the thick film active layer, and the current injection section B operates as a high-low output laser of the thin film active layer. 10 mW, 100 mW at current injection part B
Met. Therefore, it is not necessary to perform a complicated process by selective growth, and it is possible to reproduce and read and erase /
It becomes possible to realize the laser performance required for both recording.

Furthermore, according to the present invention, the wavelength 360
Since different wavelengths from nm to 650 nm can be realized only by changing the stripe width, lasers having different wavelengths can be integrated, and the problem of incompatibility of the optical disk system can be solved.

It is needless to say that the mounting method shown in FIG. 6 does not depend on the structure of the gallium nitride-based blue semiconductor laser device, and therefore can be applied to all the embodiments of the present invention. Further, the present invention is not limited to the present embodiment, and the semiconductor layer may have a different composition or a different film thickness, or may have a structure having the opposite conductivity.

[0035]

As described above in detail, according to the present invention, in a gallium nitride-based compound semiconductor laser, the active region is formed by stripes having different equivalent refractive indices, and at least one layer is formed on both sides thereof. By forming a current blocking layer made of a material having a large refractive index, a gallium nitride-based compound semiconductor laser having a reduced threshold current and oscillating in a stable fundamental transverse mode can be realized. The laser performance required as a light source can be satisfied.

According to the present invention, the current confinement structure and the light confinement structure can be easily and accurately formed by the self-alignment process. Furthermore, since the array can be easily formed by the same process, a high-output laser required for erasing and recording in the optical disk system can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram related to a first embodiment of the present invention.

FIG. 2 is a diagram related to a second embodiment of the present invention.

FIG. 3 is a diagram related to a third embodiment of the present invention.

FIG. 4 is a diagram related to a fourth embodiment of the present invention.

FIG. 5 is a diagram related to a fifth embodiment of the present invention.

FIG. 6 is a diagram related to the mounting of the semiconductor laser device according to the first embodiment of the present invention;

FIG. 7 is a diagram related to the manufacturing process of the first embodiment of the present invention.

[Explanation of symbols]

In the figure, 101, 201, 301, 401, and 501 are sapphire substrates, and 102, 202, 302, 402, and 502 are n-GaN.
The contact layers 103, 203, 303, 403, and 503 are n-Al
_0.15 Ga _0.85 N cladding layer, 104, 204, 304, 404, 504 are n-GaN
Waveguide layers, 105, 205, 307, 407, 505 are p-InG
aN current blocking layers, 106, 206, 308, 408, 506 are n-InG
aN current block layer, 107, 207, 305, 405, 507A, 508B
Are SCH-MQW active layers, 108, 208, 306, 410, 508A, 508B
Are p-GaN waveguide layers, 109, 209, 310, 410, 509A, 509B
Are p-AlGaN cladding layers, 210, 309, 409, and 411 are p-In _0.1 Ga
_0.9 N buffer layer, 110, 211, 311, 412, 510 are p-Al
_0.15 Ga _0.85 N cladding layer, 111, 212, 312, 413, 511 are p-GaN
Contact layer, 112, 213, 313, 414, 512A, 512B
Is a p-side electrode, 113, 214, 314, 415, 513 are n-side electrodes, 114, 215, 315, 416, 514 are SiO ₂ insulating films, 115 is a heat sink, 116 is a Pt / Ti / Au layer, and 117 is AuSn solder.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Yoshida 1st Toshiba R & D Center, Komukai Toshiba, Saiwai-ku, Kawasaki City, Kanagawa Prefecture No. 1 town Toshiba R & D Center

Claims (8)

[Claims] A gallium nitride-based compound semiconductor (Ga _x In)
_y Al _z B _1-xyz N: 0 ≦ x, y, z, x + y + z ≦
In a semiconductor laser comprising an active layer sandwiched between semiconductor layers of different conductivity types, a stripe-shaped current injection portion for injecting carriers into the active layer is formed, and on both sides of the current injection portion. A gallium nitride-based compound semiconductor laser, wherein at least one or more current blocking layers are formed, and the current injection portion has a structure having a different equivalent refractive index. 2. The current injection part has a structure in which an equivalent refractive index is larger at the end of the injection constriction part than at the center of the current injection part in the direction perpendicular to the stripe and the current injection direction, and the current blocking layer is formed of 2. The gallium nitride-based compound semiconductor laser according to claim 1, wherein the gallium nitride-based compound semiconductor laser is made of a gallium nitride-based compound semiconductor material having a refractive index equivalent to that of an end of the current injection portion. 3. The current injection part has a structure in which an equivalent refractive index is greater at the end of the injection constriction part than at the center of the current injection part in a direction perpendicular to the stripe and the current injection direction, and the current blocking layer is 2. The gallium nitride-based compound semiconductor laser according to claim 1, wherein the gallium nitride-based compound semiconductor laser is made of a gallium nitride-based compound semiconductor material having a large absorption loss and a large refractive index because the bandgap energy is smaller than the center of the current injection portion. 4. The current block layer is made of a gallium nitride-based compound semiconductor material, and the active layer portion is at least In _a
Ga _b Al _c B _1-abc N (0 ≦ a, b, c, a + b +
c ≦ 1) and In _e Ga _f Al _g B
_{4. A} single quantum well or multiple quantum well comprising a barrier layer made of _1-efg N ( _0≤e , f, g, e + f + _g≤1 ). The gallium nitride-based compound semiconductor laser according to the above. 5. The active layer structure according to claim 1, wherein the active layer has a plurality of active layer structures having different compositions or thicknesses or widths.
5. The gallium nitride-based compound semiconductor laser according to any one of items 1 to 4. 6. A gallium nitride based compound semiconductor (Ga _x In)
_y Al _z B _1-xyz N: 0 ≦ x, y, z, x + y + x ≦
A) a method of manufacturing a gallium nitride-based compound semiconductor laser in which an active layer is sandwiched between semiconductor layers of different conductivity types, wherein at least one or more current blocking layers are formed; And a step of forming a layer structure to be a current injection portion by selectively growing a crystal in a portion removed in the step, thereby forming a gallium nitride-based compound semiconductor laser. 7. A gallium nitride-based compound semiconductor (Ga _x In)
_y Al _z B _1-xyz N: 0 ≦ x, y, z, x + y + z ≦
1) a method of manufacturing a gallium nitride compound semiconductor laser in which an active layer is sandwiched between semiconductor layers of different conductivity types, wherein a step of selectively crystal-growing a layer structure to be a current injection portion; Forming at least one or more current blocking layers on both sides of the semiconductor laser. 8. A method for manufacturing a gallium nitride-based compound semiconductor laser according to claim 6, wherein said gallium nitride of the same conductivity type as a surface of said current injection portion is provided on said current injection portion and said current block layer. Based compound semiconductor (Ga _h
In _i Al _j B _1-hIj N: 0 ≦ h, i, j, h + i +
8. The method of manufacturing a gallium nitride-based compound semiconductor laser according to claim 6, further comprising the step of growing at least one layer of j ≦ 1).