JP3655066B2 - Gallium nitride compound semiconductor laser and manufacturing method thereof - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a semiconductor device using a nitride compound semiconductor material, and more particularly to a semiconductor laser made of an InGaAlBN material and a method for manufacturing the same.
[0002]
[Prior art]
Development of a semiconductor laser using an InGaAlN material as a short wavelength light source required for increasing the density of an optical disk is underway. A laser using a multiple quantum well structure has been reported as a structure realizing oscillation by current injection in this material system.
[0003]
It is known that a multiple quantum well structure using a thin film active layer with respect to a bulk active layer can greatly reduce the threshold value. However, in this material system, the threshold current density is still high and the operating voltage is high, so that there are many problems to realize continuous oscillation.
[0004]
One of the reasons why the operating voltage is high in the InGaAlN laser is that the p-type contact resistance is extremely large. In the already reported electrode stripe structure, the voltage drop in the p-type electrode stripe is large, the operating voltage becomes high, and the generation of heat in this region cannot be ignored. In order to reduce the contact resistance, the electrode area may be increased. However, in the above electrode stripe structure, the threshold current value increases as the electrode area is increased, and the fundamental transverse mode oscillation is not possible because the current injection region is large. Is possible.
[0005]
In application to an optical disk or the like, since it is necessary to narrow the outgoing beam to a very small spot, fundamental transverse mode oscillation is indispensable, but a transverse mode control structure is not realized in an InGaAlN laser. As a conventional material system, for example, an InGaAlP-based ridge stripe type SBR laser has been reported.
[0006]
However, since the material system is different from the InGaAlN laser, this structure cannot be applied as it is. As a current confinement structure in the InGaAlN system, Japanese Patent Application Laid-Open No. 8-111558 discloses a structure using GaN as a current confinement layer. Although this structure allows current confinement, it does not have an optical confinement function, and it is difficult to obtain a high quality outgoing beam without astigmatism.
[0007]
In general, in order for the current confinement layer provided in the clad layer to also act as a light confinement layer, it is necessary to set the composition, thickness, distance from the active layer, and the like to predetermined values. In particular, in an InGaAlN laser, since the oscillation wavelength is short, even if the composition is the same, the waveguide mechanism is completely different depending on the thickness and position. For this reason, a stable fundamental transverse mode oscillation cannot be obtained simply by providing a current confinement layer.
[0008]
On the other hand, various specifications are required for a semiconductor laser for use in an optical disk system. In particular, the write-once type and the rewritable type require a low-power semiconductor laser for reproducing and reading and a high-power semiconductor laser for erasing and recording, and the specifications are different from each other. A high-power semiconductor laser generally has a thin film active layer structure, but this structure is not necessarily suitable for a readout laser. This is because, for example, a self-oscillation type structure is used for the readout laser because low-noise characteristics are required for the readout laser, but it is difficult to obtain self-oscillation with an ultrathin active layer structure. For this reason, a high-frequency superposition method, a method using two types of lasers, and the like are used, but the configuration is complicated. Also, a method of forming two types of lasers by changing the active layer thickness depending on the location has been reported, but there is a problem that it is difficult to control the active layer thickness.
[0009]
Furthermore, as the density of optical discs increases, semiconductor lasers with different wavelengths will be used. However, compatibility with conventional optical disc systems is required, so lasers of both wavelengths are required. There is. 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 pit is lowered.
[0010]
[Problems to be solved by the invention]
Thus, conventionally, it has been difficult to produce a transverse mode control structure with an InGaAlN-based semiconductor laser, and it has been difficult to realize a semiconductor laser that continuously oscillates in a fundamental transverse mode. In addition, it has been difficult to realize the laser performance required for both reproduction / reading and erasing / recording in the optical disk system. Furthermore, it has been difficult to realize a semiconductor laser that can be used for both, which is necessary for ensuring compatibility between optical disk systems having different wavelengths and different recording densities.
[0011]
The present invention has been made in consideration of the above circumstances, and the object of the present invention is that it can continuously oscillate in a stable fundamental transverse mode, and has high quality without astigmatism suitable for a light source such as an optical disk system. An object of the present invention is to provide an InGaAlN semiconductor laser capable of obtaining an outgoing beam. Another object of the present invention is to provide a semiconductor laser capable of realizing the laser performance required for both reproduction / reading and erasing / recording in an optical disk system without requiring a difficult process, and a manufacturing method thereof. It is in.
[0012]
Still another object of the present invention is to provide a semiconductor laser that can be used for both, and a method for manufacturing the same, which are necessary for ensuring compatibility between optical disc systems having different design wavelengths.
[0013]
[Means for Solving the Problems]
The essence of the present invention is that the optical confinement layer having a large refractive index is provided, and the transverse mode is controlled by the loss waveguide effect or the anti-waveguide effect, so that the continuous oscillation in the fundamental transverse mode with a low operating voltage is stable. Is to make it possible.
[0014]
That is, the present invention relates to a gallium nitride compound semiconductor (Ga_x In_y Al_z B_1-xyz N: 0 ≦ x, y, z, x + y + z ≦ 1), and in a semiconductor laser in which an active layer is sandwiched between semiconductor layers having different conductivity types, a stripe-shaped current injection portion for injecting carriers into the active layer And at least one current blocking layer is formed on both sides of the current injection part, and the current injection part has a structure having different equivalent refractive indexes.
[0015]
Here, preferred embodiments of the present invention include the following.
(1) The current injection part has a structure in which the equivalent refractive index is larger at the end of the injection constriction part than the center of the current injection part in the direction perpendicular to the stripe and the current injection direction, and the current block layer is formed of the current injection part. It is made of a gallium nitride compound semiconductor material having a refractive index equivalent to the end.
(2) The current injection portion has a structure in which the equivalent refractive index is larger at the end of the injection constriction portion than the center of the current injection portion in the direction perpendicular to the stripe and the current injection direction, and the current blocking layer is formed of the current injection portion. It is made of a gallium nitride compound semiconductor material having a large absorption loss and a large refractive index because the band gap energy is smaller than the center.
(3) The current blocking layer is made of a gallium nitride compound semiconductor material, and the active layer portion is at least In_a Ga_b Al_c B_1-abc A well layer composed of N (0 ≦ a, b, c, a + b + c ≦ 1) and In_e Ga_f Al_g B_1-efg It consists of a single quantum well or multiple quantum wells composed of a barrier layer made of N (0 ≦ e, f, g, e + f + g ≦ 1).
[0016]
The present invention is also characterized in that a semiconductor laser that generates a plurality of laser beams has a plurality of active layer structures having different active layer compositions, thicknesses, or widths.
[0017]
The present invention also relates to a gallium nitride compound semiconductor (Ga_x In_y Al_z B_1-xyz N: 0 ≦ x, y, z, x + y + z ≦ 1), and a method of manufacturing a gallium nitride compound semiconductor laser in which an active layer is sandwiched between semiconductor layers having different conductivity types, A step of forming a layer structure to be formed, a step of selectively removing the current blocking layer, and a step of forming a layer structure to be a current injection portion by selectively crystal growth in a portion removed by the step. According to another method of the present invention, a gallium nitride-based compound semiconductor (Ga_x In_y Al_z B_{1-xy- z} N: 0.ltoreq.x, y, z, x + y + z.ltoreq.1), and a layer structure to be a current injection part is selected when manufacturing a gallium nitride compound semiconductor laser in which an active layer is sandwiched between semiconductor layers having different conductivity types. It may be a step of crystal growth and a step of forming at least one current blocking layer on both sides of the current injection portion.
[0018]
Here, as a preferred embodiment of the present invention, a gallium nitride compound semiconductor (Ga) having the same conductivity type as that of the surface of the current injection portion is formed on the block layer and the current injection portion._h In_i Al_j B_1-hIj N: 0 ≦ h, i, j, h + i + j ≦ 1) includes a step of crystal growth of at least one layer.
[0019]
According to the present invention, in the InGaAlBN semiconductor laser, the current blocking layer is provided with an optical confinement layer having a refractive index larger than that of the current injection portion, and the current injection portion has a refractive index that increases from the center toward the end to close the light. By making the confinement effect good, not only the higher-order mode is suppressed but the continuous oscillation in the stable fundamental transverse mode becomes possible, and the threshold current density can be reduced.
[0020]
Further, according to the present invention, since the low-power / low-noise laser of the thick film active layer and the high-power laser of the thin film active layer can be formed on the same substrate, reproduction and reading in the optical disk system can be performed without requiring a complicated process. Laser performance required for both erasing and recording can be realized.
Furthermore, according to the present invention, since lasers with different wavelengths can be formed on the same substrate, the problem of incompatibility due to the difference in wavelength can be solved.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The details of the present invention will be described below with reference to the illustrated embodiments.
FIG. 1 is a diagram for explaining a schematic configuration of a gallium nitride 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 + 10¹⁸cm^-34 μm), 103 is n-Al_0.15Ga_0.85N clad layer (Si doped, 1 × 10¹⁸cm^-3, 0.3 μm), 104 is an n-GaN waveguide layer (Si-doped, 0.1 μm), 105 is p-In_0.1 Ga_0.9 N (Mg doped, 1 × 10¹⁸cm^-30.2 μm) current blocking layer 106 is n-In_0.1 Ga_0.9 N (Si doped, 1 × 10¹⁸cm^-30.1 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 InGaN barrier layer sandwiching it (undoped, the center of the groove is In_0.05Ga_0.95N, 4 nm), a quantum well structure (SCH-MQW) active layer, 108 is a p-GaN waveguide layer (Mg doped, the center of the groove is 0.1 μm), 109 is p -AlGaN cladding layer (Mg doped, 1 × 10¹⁸cm^-3The center of the groove is Al_0.20Ga_0.80N, 0.1 μm), 110 is p-Al_0.15Ga_0.85N clad layer (Mg doped, 1 × 10¹⁸cm^-3, 0.3 μm), 111 is a p-GaN contact layer (Mg-doped, 1 × 10¹⁸cm^-31 μm), 112 is a Pt (10 nm) / Ti (20 nm) / Pt (30 nm) / Au (1 μm) structure p-side electrode, 113 is an Al / Ti / Au structure n-side electrode, and 114 is SiO₂ It is an insulating film. Although not shown in particular, the laser light emitting end face has TiO₂ / SiO₂ A high-reflective coating with multiple layers is applied.
[0022]
Next, a method for manufacturing the nitride compound semiconductor laser will be described with reference to the process cross-sectional view of FIG. First, as shown in FIG. 7A, an n-GaN contact layer 102 to an n-InGaN current blocking layer 106 are grown on a sapphire substrate by metal organic vapor phase epitaxy (hereinafter abbreviated as MOCVD). And SiO₂ Deposit mask and SiO₂ A part of the mask is removed in a stripe shape with a width of 7 μm.₂ Is used as an etching mask to form a groove to the n-GaN waveguide layer 104 by a dry etching method containing chlorine gas. Next, as shown in FIG.₂ As a mask, the SCH-MQW active layer 107 to the p-AlGaN cladding layer 109 are selectively grown. Where SiO₂ Since crystals do not grow on the mask, SiO2 is striped.₂ Selective growth can be performed only in the region where the film is removed. Also, striped SiO₂ The width after removing the SiO₂ When it is 1/20 or less compared to the width of the mask, SiO₂ The crystal growth rate increases as the value approaches, and as a result, the film thickness increases from the center toward the periphery. In particular, the InGaN constituting the SCH-MQW active layer 107 has an In composition that increases from the central portion toward the peripheral portion, so that the refractive index increases in a gradient manner. In the case of the first embodiment of the present invention, in the SCH-MQW active layer 107, the InGaN quantum well layer is In at the center of the stripe._0.2 Ga_0.8 N, thickness 2 nm, In at the stripe periphery_0.25Ga_0.75N, a thickness of 3 nm is formed, and the InGaN barrier layer is In at the center of the stripe._0.05Ga_0.95N, 4 nm thick, In at the stripe periphery_0.09Ga_0.91N, a thickness of 5.5 nm was formed. Next, as shown in FIG.₂ The mask is removed, and a p-AlGaN cladding layer 110 and a p-GaN contact layer 111 are grown on the entire surface. Next, as shown in FIG. 7D, a striped mesa is formed, and SiO 2 is formed on the entire surface of the wafer.₂ An insulating film 114 is deposited to 900 nm, a Pt / Ti / Pt / Au structure p-side electrode 112 is formed on the p-GaN contact layer 111, and an Al / Ti / Au structure n-side electrode is formed on a part of the n-GaN contact layer 102. 113 is formed. Next, the back surface of the sapphire substrate 101 is mirror-polished so that the thickness of the substrate 101 is 50 μm, and is further cleaved on a plane perpendicular to the current confinement structure.₂ / SiO₂ As shown in FIG. 6, a layer 116 obtained by metalizing Ti / Pt / Au or the like on a heat sink 115 having high thermal conductivity such as Cu, cubic boron nitride or diamond is applied. On the other hand, thermocompression bonding is performed using AuSn eutectic solder 117. 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, wiring is performed on the Ti / Pt / Au metallized layer 116 using Au wire or Al wire for current injection. 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, the n-GaN contact layer 102 to the n-GaN waveguide layer 104 are grown on the sapphire substrate by MOCVD, and SiO 2₂ Deposit mask and SiO₂ A part of the mask is removed in a stripe shape with a width of 7 μm, the SCH-MQW active layer 107 to the p-AlGaN cladding layer 109 are formed, and the upper portion of the p-AlGaN cladding layer 109 is formed on the SiO 2 layer.₂ Even if the n-InGaN current blocking layer 106 is formed from the p-InGaN current blocking layer 105 by covering with a mask, current injection portions having different refractive indexes in the lateral direction can be formed in the selective growth process by the MOCVD method.
[0023]
In this example, 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. Furthermore, the device lifetime at 50 ° C. and 5 mW drive was 5000 hours or more. Further, 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_0.15Ga_0.85N clad layer 110 and n-Al_0.15Ga_0.85The equivalent refractive index of the active region in which current is injected from the SCH-MQW active layer 107 to the p-AlGaN cladding layer 109 sandwiched between the N cladding layers 103 is p-In._0.1 Ga_0.9 N current blocking layer 105 to n-In_0.1 Ga_0.9 The anti-waveguide structure is lower than that of the non-current-carrying region up to the N current blocking layer 106, and the stripe-shaped current injection portion has a higher equivalent refractive index in the region close to the current blocking layer. Even if the width is not reduced, the effect of the anti-waveguide structure is increased, and the astigmatic difference is reduced because only the fundamental transverse mode is likely to exist, that is, the condition in which the primary mode of the horizontal transverse mode is cut off. Furthermore, it is clear from experiments by the inventors that InGaN has a well layer width heterogeneity of 2 nm, and the InGaN quantum well layer of the SNH-MQW active layer 107 has a 2 nm thick stripe center portion. Since the gain difference between the stripe and the peripheral portion of the stripe having a thickness of 3 nm is more difficult, the controllability of the waveguide mode is improved.
[0024]
When the In composition of the p-InGaN current blocking layer 105 and the n-InGaN current blocking layer 106 is set higher than that of the InGaN quantum well layer of the SCH-MQW active layer 107, the current blocking layers 105 and 106 absorb the oscillation wavelength. The loss increases and the attenuation of the guided mode increases, resulting in a lower equivalent refractive index of the current blocking layers 105 and 106 than the current injection portion. This case is also extremely effective for stabilizing the fundamental transverse mode. is there. This is because, since the current blocking layer is a loss region, the higher order mode with a large amount of leakage has a larger loss or cut-off than the fundamental mode, but the threshold current density is slightly lower than that of the anti-waveguide structure. To be high.
[0025]
FIG. 2 is a diagram for explaining a schematic configuration of a gallium nitride blue semiconductor laser device according to a second embodiment of the present invention. In the figure, 201 is a sapphire substrate, 202 is an n-GaN contact layer (S-doped, 5 × 10¹⁸cm^-34 μm), 203 is n-Al_0.15Ga_0.85N clad layer (Si doped, 1 × 10¹⁸cm^-3, 0.3 μm), 204 is an n-GaN waveguide layer (Si-doped, 0.1 μm), 205 is p-In_0.1 Ga_0.9 N (Mg doped, 1 × 10¹⁸cm^-30.2 μm) current blocking layer, 206 is n-In_0.1 Ga_0.9 N (Si doped, 1 × 10¹⁸cm^-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 10 layers of InGaN barrier layer sandwiching it (undoped, the center of the groove is In_0.05Ga_0.95N, 4 nm) quantum well structure (SCH-MQW) active layer, 208 is a p-GaN waveguide layer (Mg doped, groove center is 0.1 μm), 209 is a p-AlGaN cladding layer (Mg doped, 1 × 10¹⁸cm^-3The center of the groove is Al_0.20Ga_0.80N, 20 nm), 210 is p-In_0.25Ga_0.75N layer (Mg doped, 1 × 10¹⁸cm^-3, 50 nm), 211 is p-Al_0.15Ga_0.85N clad layer (Mg doped, 1 × 10¹⁸cm^-3, 0.3 μm), 212 is a p-GaN contact layer (Mg-doped, 1 × 10¹⁸cm^-31 μm), 213 is a Pt (10 nm) / Ti (20 nm) / Pt (30 nm) / Au (1 μm) structure p-side electrode, 214 is an Al / Ti / Au structure n-side electrode, and 215 is SiO₂ It is an insulating film. Although not shown in particular, the laser light emitting end face has TiO₂ / SiO₂ A high-reflective coating with multiple layers is applied.
[0026]
This embodiment differs from Example 1 of the present invention shown in FIG. 1 in that p-In_0.25Ga_0.75The N layer 211 is inserted. In the case of this laser, the p-AlGaN cladding layer 209 and n-In exposed to the atmosphere in the manufacturing process._0.1 Ga_0.9 P-In is applied to each surface of the N current blocking layer 206 from a relatively low temperature._0.25Ga_0.75Since the growth of the N layer 211 can be started, the p-AlGaN cladding layer 209 and the n-In_0.1 Ga_0.9 In addition to being able to prevent evaporation of constituent elements from the surface of the N current blocking layer 206, p-In_0.25Ga_0.75Since the N layer 211 functions as a saturable absorption layer, the beam characteristics are improved.
[0027]
FIG. 3 is a diagram for explaining a schematic configuration of a gallium nitride blue semiconductor laser device according to a third embodiment of the present invention. In the figure, 301 is a sapphire substrate, 302 is an n-GaN contact layer (Si-doped, 5 × 10¹⁸cm^-34 μm), 303 is n-Al_0.15Ga_0.85N clad layer (Si doped, 1 × 10¹⁸cm^-3, 0.3 μm), 304 is an n-GaN waveguide layer (Si-doped, 0.1 μm), 305 is In_0.2 Ga_0.8 N quantum well (undoped, 2nm) with 10 layers and In_0.05Ga_0.95Quantum 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 Ga_0.9 N (Si doped, 1 × 10¹⁸cm^-3, 0.2 μm) current blocking layer, 308 is n-Al_0.15Ga_0.85N (Si doped, 1 × 10¹⁸cm^-3, 0.1 μm), current blocking layer 309 is p-In_0.25Ga_0.75N layer (Mg doped, 1 × 10¹⁸cm^-3, 50 nm), 310 is Al_0.20Ga_0.80N clad layer (Mg doped, 1 × 10¹⁸cm^-3, 0.1 μm), 311 is p-Al_0.15Ga_0.85N clad layer (Mg doped, 1 × 10¹⁸cm^-3, 0.3 μm), 312 is a p-GaN contact layer (Mg-doped, 1 × 10¹⁸cm^-31 μm), 313 is a 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, and 315 is SiO₂ It is an insulating film. Although not shown in particular, the laser light emitting end face has TiO₂ / SiO₂ A high-reflective coating with multiple layers is applied.
[0028]
In the case of the laser of this example, p-Al_0.15Ga_0.85P-In sandwiched between the N-clad layer 311 and the p-GaN waveguide layer 306_0.25Ga_0.75N layer 309 and Al_0.20Ga_0.80The current injection part made of the N clad layer 310 is p-In._0.1 Ga_0.9 N current blocking layer 307 and n-Al_0.15Ga_0.85The equivalent refractive index is lower than that of the current blocking layer made of the N current blocking layer 308 to form an anti-waveguide structure, and the refractive index is lower in the central portion of the current injection portion than in the peripheral portion. Accordingly, as in the first embodiment of the present invention, the horizontal / horizontal mode is only the basic mode, and the astigmatic difference is reduced.
[0029]
FIG. 4 is a view for explaining a schematic configuration of a gallium nitride blue semiconductor laser device according to a fourth embodiment of the present invention. In the figure, 401 is a sapphire substrate, 402 is an n-GaN contact layer (Si-doped, 5 × 10¹⁸cm^-34 μm), 403 is n-Al_0.15Ga_0.85N clad layer (Si doped, 1 × 10¹⁸cm^-3, 0.3 μm), 404 is an n-GaN waveguide layer (Si-doped, 0.1 μm), 405 is In_0.2 Ga_0.8 N quantum well (undoped, 2nm) with 10 layers and In_0.05Ga_0.95Quantum 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), and 407 is n-In_0.1 Ga_0.9 N (Si doped, 1 × 10¹⁸cm^-30.2 μm), current blocking layer, 408 is n-Al_0.15Ga_0.85N (Si doped, 1 × 10¹⁸cm^-3, 0.1 μm) current blocking layer, 409 is p-In_0.25Ga_0.75N layer (Mg doped, 1 × 10¹⁸cm^-3, 50 nm), 410 is Al_0.20Ga_0.80N clad layer (Mg doped, 1 × 10¹⁸cm^-3, 0.1 μm), 411 is p-In_0.25Ga_0.75N layer (Mg doped, 1 × 10¹⁸cm^-3, 50 nm), 412 is p-Al_0.15Ga_0.85N clad layer (Mg doped, 1 × 10¹⁸cm^-30.3 μm), 413 is a p-GaN contact layer (Mg-doped, 1 × 10¹⁸cm^-31 μm), 414 is Pt (10 nm) / Ti (20 nm) / Pt (30 nm) / Au (1 μm) structure p-side electrode, 415 is Al / Ti / Au structure n-side electrode, 416 is SiO₂ It is an insulating film. Although not shown in particular, the laser light emitting end face has TiO₂ / SiO₂ A high-reflective coating with multiple layers is applied.
[0030]
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 the same manner as p-In._0.25Ga_0.75The N layer 411 is inserted. Accordingly, as in the second embodiment of the present invention, since the burying growth can be performed from a low temperature, the underlying layer can be prevented from being altered.
[0031]
FIG. 5 is a diagram for explaining a schematic configuration of a gallium nitride blue semiconductor laser device according to a fifth embodiment of the present invention. In the figure, 501 is a sapphire substrate, 502 is an n-GaN contact layer (Si-doped, 5 × 10¹⁸cm^-34 μm), 503 is n-Al_0.15Ga_0.85N clad layer (Si doped, 1 × 10¹⁸cm^-3, 0.3 μm), 504 is an n-GaN waveguide layer (Si-doped, 0.1 μm), 505 is p-In_0.1 Ga_0.9 N (Mg doped, 1 × 10¹⁸cm^-30.2 μm) current blocking layer, 506 is n-In_0.1 Ga_0.9 N (Si doped, 1 × 10¹⁸cm^-30.1 μm) current blocking layer, 507A and 507B are InGaN quantum wells (undoped, the center of the groove is In_0.3 Ga_0.7 N, 4nm and In_0.2 Ga_0.8 N, 2 nm) and 10 layers of InGaN barrier layers sandwiching it (undoped, the center of the groove is In_0.1 Ga_0.9 N, 8nm and In_0.05Ga_0.95N, 4 nm) quantum well structure (SCH-MQW) active layer, 508A and 508B are p-GaN waveguide layers (Mg doped, the center of the groove is 0.1 μm and 0.06 μm, respectively), and 509A and 509B are p-AlGaN cladding layer (Mg doped, 1 × 10¹⁸cm^-3The center of the groove is Al_0.20Ga_0.80N and film thickness are 0.1 μm and 0.06 μm, respectively, 510 is p-Al_0.15Ga_0.85N clad layer (Mg doped, 1 × 10¹⁸cm^-3, 0.3 μm), 511 is a p-GaN contact layer (Mg-doped, 1 × 10¹⁸cm^-31 μm), 512 is a Pt (10 nm) / Ti (20 nm) / Pt (30 nm) / Au (1 μm) structure p-side electrode, 513 is an Al / Ti / Au structure n-side electrode, and 514 is SiO₂ It is an insulating film. Although not shown in particular, the laser light emitting end face has TiO₂ / SiO₂ A high-reflective coating with multiple layers is applied.
[0032]
The present embodiment is different from the first embodiment of the present invention shown in FIG. 1 in that there are two types of current injection portions of 5 μm and 10 μm. SiO₂ In the formation of the SCH-MQW active layers 507A and 507B by selective growth using a mask, the composition of the InGaN quantum well layer that determines the laser oscillation wavelength increases and the film thickness increases as the stripe width decreases. Therefore, at the center of the current injection portion A having a stripe width of 5 μm, In_0.3 Ga_0.7 N, a 4 nm quantum well layer is formed, and the center of the current injection portion B having a stripe width of 10 μm is In._0.2 Ga_0.8 N and 2 nm quantum well layers were formed and oscillated at wavelengths of 425 nm and 420 nm, respectively. In the case of this laser, the current injection part A operates as a low-power / low-noise laser of the thick film active layer, the current injection part B operates as a high-low power laser of the thin film active layer, and the maximum light output is from the current injection part A. 10 mW and 100 mW at the current injection portion B. Therefore, it is possible to realize the laser performance required for both reproduction reading and erasing / recording in the optical disc system without requiring a complicated process by selective growth.
[0033]
Furthermore, according to the present invention, different wavelengths from a wavelength of 360 nm to a wavelength of 650 nm can be realized only by changing the stripe width, so that lasers with different wavelengths can be integrated, and the incompatibility of the optical disk system Can solve the problem.
[0034]
Note that the mount method shown in FIG. 6 does not depend on the structure of the gallium nitride blue semiconductor laser device, and needless to say, it can be applied to all 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 film thickness, or may have a structure with reverse conductivity.
[0035]
【The invention's effect】
As described above in detail, according to the present invention, in the gallium nitride compound semiconductor laser, the active region is formed by stripes having different equivalent refractive indexes, and at least one layer on each side has a large refractive index. By forming a current blocking layer made of a material, it is possible to realize a gallium nitride compound semiconductor laser that reduces the threshold current and oscillates in a stable fundamental transverse mode, and is required as a light source for an optical disk system or the like. It becomes possible to satisfy the laser performance.
[0036]
Further, according to the present invention, a current confinement structure and an optical confinement structure can be formed easily and accurately by a self-alignment process. Furthermore, since the array can be easily formed by the same process, a high-power laser required for erasing / recording of 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 relating to the mounting of the semiconductor laser device of 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, 501 are sapphire substrates,
102, 202, 302, 402, 502 are n-GaN contact layers
103, 203, 303, 403 and 503 are n-Al_0.15Ga_0.85N clad layer,
104, 204, 304, 404, 504 are n-GaN waveguide layers,
105, 205, 307, 407 and 505 are p-InGaN current blocking layers,
106, 206, 308, 408, 506 are n-InGaN current blocking layers,
107, 207, 305, 405, 507A, 508B are SCH-MQW active layers,
108, 208, 306, 410, 508A and 508B are p-GaN waveguide layers,
109, 209, 310, 410, 509A, 509B are p-AlGaN cladding layers,
210, 309, 409, 411 are p-In_0.1 Ga_0.9 N buffer layer,
110, 211, 311, 412, 510 are p-Al_0.15Ga_0.85N clad layer,
111, 212, 312, 413, 511 are p-GaN contact layers,
112, 213, 313, 414, 512A, 512B are p-side electrodes,
113, 214, 314, 415 and 513 are n-side electrodes,
114, 215, 315, 416, 514 is SiO₂ Insulation film,
115 is a heat sink,
116 is a Pt / Ti / Au layer;
117 is AuSn solder.

Claims (8)

In a semiconductor laser made of a gallium nitride compound semiconductor (Ga _x In _y Al _z B _1-xyz N: 0 ≦ x, y, z, x + y + z ≦ 1), the active layer is sandwiched between semiconductor layers having different conductivity types, the active layer stripe-shaped current injection part for injecting carriers is formed, on both sides of the current injection portion being at least one layer of the current blocking layer is formed, said current injection portion is a stripe and the current A gallium nitride-based compound semiconductor laser having a structure in which an equivalent refractive index in a direction perpendicular to an injection direction is larger at an end of the current injection portion than at a center of the current injection portion . Said current blocking layer is said current injection portion end than the equivalent to Claim 1 gallium nitride-based compound semiconductor laser, wherein the refractive index is made of large gallium nitride compound semiconductor material. It said current blocking layer is said current injection portion Claim 1 gallium nitride-based compound according semiconductor band gap energy than center smaller rather absorption loss is characterized in that it consists of large and refractive index is large gallium nitride-based compound semiconductor material laser. Wherein the current block layer is composed of a gallium nitride 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 claims, wherein the _{in e Ga f Al g B 1} -efg N (0 ≦ e, f, g, e + f + g ≦ 1) that consists of a single quantum well or multiple quantum well composed to consist barrier layer Item 4. The gallium nitride compound semiconductor laser according to any one of Items 1 to 3.   5. The gallium nitride compound semiconductor laser according to claim 1, wherein there are a plurality of active layer structures having different compositions, thicknesses, or widths of the active layer. 2. The current injection portion includes an active layer having a thickness and a high In composition at the end of the current injection portion in the direction perpendicular to the stripe and the current injection direction from the center of the current injection portion. The gallium nitride compound semiconductor laser according to any one of? Gallium nitride compound semiconductor _{(Ga x In y Al z B} 1-xyz N: 0 ≦ x, y, z, x + y + x ≦ 1) consists, viewed挾the active layer in semiconductor layers having different conductivity types, said active layer In a method of manufacturing a gallium nitride compound semiconductor laser having a stripe-shaped current injection portion for injecting carriers, a step of forming at least one current block layer and selectively removing the current block layer a step of a layer structure serving as the current injection portion and the portion removed by the process, the stripe and the current injection direction perpendicular to the equivalent refractive index is large at the end of the current injection portion than the center of the current injection section A step of selectively growing a crystal so as to form a structure, and a gallium nitride compound semiconductor (Ga _h) having the same conductivity type as the surface of the current injection portion on the current injection portion and the current blocking layer. A method of manufacturing a gallium nitride-based compound semiconductor laser comprising a step of crystal growth of at least one layer of In _i Al _j B _1-hij N: 0 ≦ h, i, j, h + i + j ≦ 1) . Gallium nitride compound semiconductor _{(Ga x In y Al z B} 1-xyz N: 0 ≦ x, y, z, x + y + z ≦ 1) consists, viewed挾the active layer in semiconductor layers having different conductivity types, said active layer in striped current injection portion is a manufacturing method of the formed gallium nitride-based compound semiconductor laser for injecting carriers, said current injection portion and comprising a layer structure, the equivalent refractive index in a direction perpendicular to the stripe and the current injection direction A step of selectively growing a crystal so as to have a larger structure at the end of the current injection portion than the center of the current injection portion; and a step of forming at least one current blocking layer on both sides of the current injection portion ; the on top of the current injection portion and the current blocking layer, said current injection portion of the surface of the same conductivity type gallium nitride compound semiconductor _{(Ga h in i Al j B} 1-hij N: 0 ≦ h, i, j, h + i method for producing a gallium nitride-based compound semiconductor laser, characterized in that it comprises a j ≦ 1) a step of crystal growth at least one layer.

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