JP3562455B2 - Method of forming nitride semiconductor laser device - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a nitride semiconductor (In _X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1).
[0002]
[Prior art]
Nitride semiconductors have been studied as materials for semiconductor lasers that oscillate from ultraviolet to blue, but no reports have been made until recently that oscillation was actually successful. However, in December 1995, we announced the world's first pulse oscillation at room temperature of 410 nm with a laser device made of this material.
[0003]
[Problems to be solved by the invention]
The device that succeeded in pulse oscillation is a gain-guided laser device in which a stripe-shaped electrode is used as a positive electrode and the current related to the active layer is limited by the electrode width, and has a threshold current density of 4 kA / cm 2 or more. For continuous oscillation, it is necessary to further reduce the threshold current density.
[0004]
Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to reduce the threshold current of a laser device made of a nitride semiconductor and to achieve a device capable of continuous oscillation at room temperature. It is to realize.
[0005]
[Means for Solving the Problems]
The method for forming a laser device according to the present invention includes the steps of: P-type cap layer in contact with the In-containing nitride semiconductor layer of the active layer A method of forming an effective refractive index type nitride semiconductor laser device having at least a p-type light guide layer, a p-type light confinement layer and a p-type contact layer, wherein the p-type cap layer contains Al The p-type light guide layer is made of a p-type In-containing nitride semiconductor or GaN, and the p-type light confinement layer is made of a p-type nitride containing Al. The p-type contact layer is made of p-type InGaN or GaN, and the width of the p-type nitride semiconductor layer in a direction parallel to a resonance direction of the nitride semiconductor laser device is set to the active width. Forming a nitride semiconductor laser device having a step of etching so that at least a part of the p-type cap layer remains at a depth smaller than the width of the layer and not exceeding the active layer. It is a method.
[0006]
Further, in the method of forming a nitride semiconductor laser device according to claim 2, the cross-sectional shape of the etched p-type nitride semiconductor layer is such that the active layer side is a bottom portion with respect to a direction perpendicular to a laser light resonance direction. And a step of etching into a trapezoid with the contact layer side as the upper part. A third aspect of the present invention is characterized in that the p-type cap layer is doped with Mg. According to a fourth aspect, the p-type cap layer is Film thickness 10 .ANG. Or more and 1 .mu.m or less, wherein the p-type cap layer is Film thickness The thickness is not less than 100 Å and not more than 0.1 μm.
[0007]
[Action]
A nitride semiconductor has a property that it is difficult to grow a thick film. For example, a nitride semiconductor containing Al has particularly strong properties. For laser oscillation, it is important to grow an active layer having good crystallinity. In the present invention, since the active layer is made of a nitride semiconductor containing In, its crystal properties are softer than those of other nitride semiconductors containing Al, so that a thick film can be easily grown and an active layer with good crystallinity can be formed. it can. Further, an optical guide layer made of a p-type nitride semiconductor is provided on the active layer. In the case of a GaAlAs-based semiconductor laser, the light guide layer can also be used as the active layer, which is not particularly necessary. However, in the case of a nitride semiconductor, as described above, it is difficult to grow a thick film, so this light guide layer is essential. The next light confinement layer may be any layer as long as it has a band gap larger than that of the active layer. In order to make the band gap larger than that of the active layer, a nitride semiconductor containing Al is selected. However, since a p-type nitride semiconductor containing Al is difficult to form an ohmic contact with an electrode, a contact layer is essential.
[0008]
In addition, the width of the light guide layer, the light confinement layer, and the contact layer in the direction parallel to the resonance direction of the laser light of the laser element is adjusted to be smaller than the width of the active layer by etching, so that a so-called effective refractive index waveguide type is used. Laser element. With such a structure, the current can be concentrated on one point of the active layer without spreading in the p-type layer above the active layer, and light can be concentrated only on the active portion below the p-type layer. Mode laser light can be confined, and the threshold current can be reduced.
[0009]
Furthermore, if a positive electrode is formed via an insulating thin film, the insulating thin film protects the etched surfaces of the light guide layer, the optical confinement layer, and the contact layer, and a large-area positive electrode is formed directly on the etched contact layer. can do. Further, even in a nitride semiconductor laser device in which the positive and negative electrodes are provided on the same surface side, a short circuit between both electrodes can be prevented by interposing an insulating thin film.
[0010]
Next, the cross-sectional shape of the etched optical guide layer, optical confinement layer, and contact layer is trapezoidal with the active layer side at the bottom and the contact layer side at the top with respect to the direction perpendicular to the laser light resonance direction. An insulating thin film having a uniform thickness and no pits or defects can be formed. If the insulating thin film has pits or defects, the electrode material may enter the pits when the electrodes are formed by CVD or the like, and may cause an electrical short circuit of the device.
[0011]
The active layer is In _X Ga _1-X It has a multiple quantum well structure having a well layer composed of N (0 <X <1). InGaN can be grown with good crystallinity. In _X Ga _1-X The thickness of the well layer made of N is desirably 100 angstroms or less, and more desirably 70 angstroms or less. In the case of a multiple quantum well structure, a barrier layer is also stacked, but InGaN or GaN having a larger band gap than the well layer is selected. Particularly preferably, when the barrier layer is also made of InGaN, both the well layer and the barrier layer are made of InGaN. Therefore, the GaN layer can be grown at the same temperature, so that it is not necessary to raise the temperature as in the case of forming GaN, and the previously formed InGaN well layer is hardly decomposed. As a result, the overall crystallinity of the multiple quantum well structure is improved, so that laser oscillation can be easily performed. Although the thickness of the barrier layer is not particularly limited, it is preferable that the thickness be equal to or less than twice the thickness of the well layer.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic sectional view showing the structure of a laser device according to one embodiment of the present invention, and FIG. 2 is a perspective view showing the shape of the laser device of FIG. FIG. 1 is a cross-sectional view of the device shown in FIG. 2 taken along a direction perpendicular to the laser light resonance direction. As an element structure, an n-type contact layer 2, an n-type light confinement layer 3, an n-type light guide layer 4, an active layer 5, a p-type light guide layer 6, a p-type light confinement layer 7, It has a basic structure in which the mold contact layers 8 are sequentially stacked. It should be noted that the structure of the laser element described in this specification shows only a basic structure, and even if a layer made of another nitride semiconductor is inserted between the layers shown in the description, the structure of the present invention is not limited to the claims. Modifications may be made as appropriate as long as they do not depart from the idea shown.
[0013]
As the substrate 1, an insulating substrate such as sapphire (Al2O3, A-plane, C-plane, and R-plane) and spinel (MgAl2O4, 111-plane) are often used. In addition, the substrate 1 is made of a single crystal such as SiC, MgO, Si, or ZnO. A conventionally known substrate is used.
[0014]
The n-type contact layer 2 is made of In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1). In particular, by using GaN, InGaN, and especially GaN doped with Si, an n-type layer having a high carrier concentration can be obtained. Further, since a preferable ohmic contact with the negative electrode 20 is obtained, the threshold current of the laser device can be reduced. As a material for the negative electrode 20, a metal or alloy such as Al, Ti, W, Cu, Zn, Sn, and In can be used to obtain an ohmic. Not only GaN but also nitride semiconductors have the property of being n-type due to nitrogen vacancies formed inside the crystal even when they are non-doped (in a state where impurities are not doped). However, donor impurities such as Si, Ge, and Sn are added during crystal growth. By doping, a nitride semiconductor having a high carrier concentration and exhibiting preferable n-type characteristics can be obtained.
[0015]
The n-type optical confinement layer 3 is made of an n-type nitride semiconductor containing Al, and is preferably a binary or ternary mixed Al. _Y Ga _1-Y By setting N (0 <Y ≦ 1), a crystal having good crystallinity can be obtained, and the difference in refractive index from the active layer is increased, which is effective for confining the longitudinal mode of laser light. This layer is usually preferably grown to a thickness of 0.1 μm to 1 μm. When the thickness is less than 0.1 μm, it does not easily function as a light confinement layer.
[0016]
The n-type light guide layer 4 is made of an n-type nitride semiconductor containing In or n-type GaN, and preferably has a ternary mixed crystal or binary mixed crystal InXGa1-XN (0 ≦ X <1). This layer is usually preferably grown to a thickness of 100 Å to 1 μm. In particular, by using InGaN or GaN, the next active layer 5 can easily have a quantum well structure.
[0017]
As described above, the active layer 5 is formed of a nitride semiconductor containing In, and is preferably a ternary mixed crystal of In. _X Ga _1-X N (0 <X <1). Since ternary mixed crystal InGaN has better crystallinity than quaternary mixed crystal, luminescence output is improved. Among them, particularly preferably, the active layer has a multiple quantum well structure (MQW: Multi-quantum-well) in which a well layer made of InXGa1-XN and a barrier layer made of a nitride semiconductor having a larger band gap than the well layer are stacked. I do. Similarly, the barrier layer is preferably a ternary mixed crystal InX'Ga1-X'N (0≤X '<1, X'<X), and is formed as a well + barrier + well +... + Barrier + well layer. To form a multiple quantum well structure. As described above, when the active layer is an MQW in which InGaN is stacked, a high-power LD in the range of about 365 nm to 660 nm can be realized by quantum level emission. Further, when a barrier layer made of InGaN is stacked on the well layer, the barrier layer made of InGaN has a softer crystal than GaN and AlGaN crystals. Therefore, the thickness of AlGaN in the cladding layer can be increased, so that laser oscillation can be realized. Further, InGaN and GaN have different crystal growth temperatures. For example, in the MOVPE method, InGaN is grown at 600 ° C. to 800 ° C., whereas GaN is grown at a temperature higher than 800 ° C. Therefore, in order to grow a barrier layer made of GaN after growing a well layer made of InGaN, it is necessary to raise the growth temperature. If the growth temperature is increased, the previously grown InGaN well layer is decomposed, so that it is difficult to obtain a well layer having good crystallinity. Further, the thickness of the well layer is only several tens of angstroms, and it becomes difficult to manufacture the MQW when the well layer of the thin film is decomposed. On the other hand, in the present invention, since the barrier layer is also made of InGaN, the well layer and the barrier layer can be grown at the same temperature. Therefore, since the well layer formed earlier does not decompose, an MQW with good crystallinity can be formed. This shows the most preferable mode of the MQW. However, any other composition such as InGaN for the well layer, GaN for the barrier layer, or AlGaN, in which the bandgap energy of the barrier layer is larger than that of the well layer, may be used. good.
[0018]
The total thickness of the active layer 5 having a multiple quantum well structure is preferably adjusted to 100 Å or more. If the thickness is less than 100 angstroms, the output does not increase sufficiently, and laser oscillation tends to be difficult. If the thickness of the active layer is too large, the output tends to decrease, and it is desirable that the thickness be adjusted to 1 μm or less, more preferably 0.5 μm or less. If the thickness is more than 1 μm, the crystallinity of the active layer is deteriorated, or the laser light spreads in the active layer, and the threshold current tends to increase.
[0019]
Next, the p-type light guide layer 6 is made of a nitride semiconductor containing In or GaN, and preferably grows a binary or ternary mixed InYGa1-YN (0 <Y ≦ 1). The light guide layer 6 is preferably grown with a thickness of usually 100 Å to 1 μm. In particular, by using InGaN or GaN, the next p-type light confinement layer 7 can be grown with good crystallinity. Note that a p-type nitride semiconductor can be obtained by doping an acceptor impurity such as Zn, Mg, Be, Cd, or Ca during crystal growth, and Mg exhibits the most preferable p-type characteristics. After the crystal growth, annealing is performed at 400 ° C. or more in an inert gas atmosphere to obtain a p-type with lower resistance.
[0020]
The p-type optical confinement layer 7 is made of a p-type nitride semiconductor containing Al, and is preferably a binary mixed crystal or a ternary mixed crystal Al _Y Ga _1-Y By setting N (0 <Y ≦ 1), a material having good crystallinity can be obtained. This p-type optical confinement layer is preferably grown to a thickness of 0.1 μm to 1 μm, similarly to the n-type optical confinement layer, and by using an Al-containing p-type nitride semiconductor such as AlGaN, And effectively acts as a light confinement layer for longitudinal mode laser light.
[0021]
The p-type contact layer 8 is a p-type In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1). In particular, when InGaN and GaN, among them, p-type GaN doped with Mg, a p-type layer having the highest carrier concentration can be obtained. As a result, good ohmic contact with the positive electrode 30 is obtained, and the threshold current can be reduced. As the material of the positive electrode 30, a metal or alloy having a relatively high work function such as Ni, Pd, Ir, Rh, Pt, Ag, and Au can easily obtain an ohmic.
[0022]
The basic structure of the laser device of the present invention has been described above. _X Ga _1-X Al of N and p-type layers _X Ga _1-X The composition ratio X value of N or the like merely indicates a general formula, and X of the n-type layer and X of the p-type layer do not indicate the same value. Similarly, the Y value used in other general formulas does not indicate the same value in the same general formula.
[0023]
Next, in the laser device of the present invention, the p-type light guide layer 6, the p-type light confinement layer 7, and the p-type contact layer 8 in the direction horizontal to the resonance direction of the laser beam are etched to be wider than the width of the active layer 5. Narrowed. As the etching means, dry etching is preferably used, and for example, reactive ion etching, ion milling, ECR etching, focused ion beam etching, ion beam assisted etching and the like can be used. When the preferred width of the etched p-type layer is adjusted to 10 μm or less, more preferably 5 μm or less, and most preferably 3 μm or less, the astigmatic difference of the laser decreases and the threshold current decreases. In FIG. 1, the end face is vertically etched by these etching means, but it is more preferable that the cross-sectional shape after the etching be trapezoidal by mesa etching.
[0024]
Next, in order to form the insulating thin film 10, a commonly used gas-phase film forming means such as plasma CVD, sputtering, or molecular beam deposition can be used. As a material of the insulating thin film 10, for example, a high dielectric material such as SiO2, SiN, AlN, and Al2O3 can be used. Although the thickness of the insulating thin film is not particularly limited, it can be formed, for example, with a thickness of about 0.01 μm to 50 μm.
[0025]
As a technique similar to the present invention, for example, Japanese Patent Application Laid-Open No. 6-152072 discloses a refractive index guided laser element. However, in this publication, the etching depth reaches the n-type layer beyond the active layer. In the laser device of the present invention, the etching depth does not exceed the active layer as shown in FIGS. By not exceeding the active layer, etching damage hardly enters the active layer, so that the life of the laser element can be extended.
[0026]
The positive electrode 30 is connected to the p-type contact layer 8 via the insulating thin film 10. In this figure, the electrode is formed directly above the p-type contact layer 8, but as shown in FIG. 3, the positive electrode 30 may be extended via the insulating thin film 10 in order to increase the electrode area. .
[0027]
FIG. 3 is a schematic sectional view showing the structure of a laser device according to another embodiment of the present invention. In this figure, the etched cross-sectional shapes of the p-type light guide layer 6, the p-type light confinement layer 7, and the p-type contact layer 8 are such that the active layer 5 side is the bottom with respect to the direction perpendicular to the laser light resonance direction. , The trapezoid having the p-type contact layer 8 side as the upper part. As shown in FIG. 1, when the etched end face has a substantially vertical shape, pits (holes) are easily generated in the insulating thin film formed on the etched face. In other words, it is more difficult to form a uniform film in a portion corresponding to a right angle portion and a vertical portion generated by etching than in a horizontal portion. If the metal material serving as the positive electrode intrudes from the pit, there is a possibility that a short circuit occurs. However, if the shape is as shown in FIG. 3, the insulating thin film 10 can be formed with a uniform thickness, so that the reliability of the element is improved. It is desirable that the stripe width of the uppermost p-type contact layer mesa-etched in a trapezoid is also adjusted to 10 μm or less, more preferably 5 μm or less, and most preferably 3 μm or less. Further, as shown in FIG. 3, the etching depth can be stopped in the middle of the p-type light guide layer 6 without etching until reaching the active layer 5 as shown in FIG. Further, the area of the positive electrode 30 can also be increased in order to wire bond or directly bond the laser element to a heat sink or a submount.
[Example]
FIG. 4 is a schematic sectional view showing the structure of a laser device according to one embodiment of the present invention. Hereinafter, a specific example of the present invention will be described with reference to FIG. Although the method of the embodiment is a method of manufacturing an LD device by the MOVPE method, the device of the present invention is not limited to the MOVPE method, but may be another known nitride semiconductor such as MBE, HDVPE or the like. Can be used to grow.
[0028]
After the well-washed spinel substrate 41 (MgAl2O4, 111 surface) is placed in the reaction vessel of the MOVPE apparatus, TMG (trimethylgallium) and ammonia are used as source gases, and GaN is applied to the surface of the sapphire substrate at a temperature of 500 ° C. The buffer layer 42 was grown to a thickness of 200 angstroms. The buffer layer 41 has an effect of alleviating lattice mismatch between the substrate and the nitride semiconductor, and can also grow AlN, AlGaN, or the like. It is known that the growth of the buffer layer improves the crystallinity of the n-type nitride semiconductor grown on the substrate, but the buffer layer may not be grown depending on the growth method, the type of the substrate, and the like. .
[0029]
Subsequently, the temperature was increased to 1050 ° C., and an n-type contact layer 43 made of Si-doped GaN was grown to a thickness of 4 μm using TMG, ammonia as a source gas, and SiH 4 (silane) gas as a donor impurity.
[0030]
Next, the temperature is lowered to 750 ° C., and a crack prevention layer 44 made of Si-doped In0.1Ga0.9N is grown to a thickness of 500 angstrom using TMG, TMI (trimethylindium), ammonia, and silane gas as impurity gases. I let it. The crack prevention layer 44 is grown from an n-type nitride semiconductor containing In, preferably InGaN, so that an n-type optical confinement layer 45 made of a nitride semiconductor containing Al to be grown next is grown as a thick film. Becomes possible. In the case of LD, it is necessary to grow a layer to be a light confinement layer and a light guide layer with a thickness of, for example, 0.1 μm or more. Conventionally, when thick AlGaN was directly grown on a GaN or AlGaN layer, cracks were formed in the AlGaN grown later, making it difficult to fabricate the device. Cracks can be prevented from entering the layer 45. Moreover, even if the optical confinement layer 45 to be grown next is grown as a thick film, it can be grown with good film quality. Preferably, the crack prevention layer 44 is grown to a thickness of 100 Å or more and 0.5 μm or less. If it is thinner than 100 Å, it will be difficult to act as a crack prevention as described above, and if it is thicker than 0.5 μm, the crystal itself tends to turn black. The crack prevention layer 44 can be omitted depending on the growth method and the growth apparatus.
[0031]
Next, the temperature was set to 1050 ° C., and the n-type optical confinement layer 45 made of Si-doped n-type Al0.3Ga0.7N was reduced to 0 using TEG, TMA (trimethylaluminum), ammonia as the source gas, and silane gas as the impurity gas. It was grown to a thickness of 0.5 μm.
[0032]
Subsequently, an n-type optical guide layer 46 made of Si-doped n-type GaN was grown to a thickness of 500 angstrom using TMG and ammonia as source gases and silane gas as an impurity gas.
[0033]
Next, the active layer 47 was grown using TMG, TMI, and ammonia as source gases. The temperature of the active layer is maintained at 750 ° C., and first a well layer made of non-doped In0.2Ga0.8N is grown to a thickness of 25 Å. Next, a barrier layer made of non-doped In0.01Ga0.95N is grown to a thickness of 50 angstroms at the same temperature only by changing the molar ratio of TMI. This operation was repeated 13 times, and finally a well layer was grown to grow an active layer 47 having a multiple quantum well structure with a total thickness of 0.1 μm.
[0034]
After the growth of the active layer 47, the temperature is raised to 1050 ° C., and a p-type cap layer 48 made of Mg-doped p-type Al0.2Ga0.8N is formed using Tp, TMA, ammonia and Cp2Mg (cyclopentadienyl magnesium) as an acceptor impurity source. It was grown to a thickness of 100 Å. By growing this p-type cap layer 48 to a thickness of 1 μm or less, more preferably 10 angstrom or more and 0.1 μm or less, the p-type cap layer 48 has a function as a cap layer for preventing the active layer made of InGaN from being decomposed. Further, by growing the p-type cap layer 48 made of a p-type nitride semiconductor containing Al on the active layer, the light emission output is significantly improved. Conversely, if the p-layer in contact with the active layer is GaN, the output of the device will be reduced to about 1/3. This is presumed to be due to the fact that AlGaN is more likely to be p-type than GaN, and has the effect of suppressing the decomposition of InGaN during growth of the p-type cap layer 48, but the details are unknown. If the thickness of the p-type cap layer 48 is greater than 1 μm, cracks tend to occur in the layer itself, which tends to make element fabrication difficult. The p-type cap layer 48 can be omitted.
[0035]
Next, while maintaining the temperature at 1050 ° C., a p-type optical guide layer 49 made of Mg-doped p-type GaN was grown to a thickness of 500 Å using TMG, ammonia and Cp2Mg. As described above, by using InGaN or GaN for the second p-type light guide layer 49, the following light confinement layer 50 containing Al can be grown with good crystallinity.
[0036]
Subsequently, a p-type optical confinement layer 50 made of Mg-doped Al0.3Ga0.7N was grown to a thickness of 0.5 μm using TMG, TMA, ammonia, and Cp2Mg.
[0037]
Subsequently, a p-type contact layer 51 made of Mg-doped p-type GaN was grown to a thickness of 0.5 μm using TMG, ammonia, and Cp2Mg.
[0038]
The wafer on which the nitride semiconductor is laminated as described above is taken out of the reaction vessel, and the reactive ion etching (RIE) apparatus is used to perform selective etching from the uppermost p-type contact layer 51 to form the negative electrode 20. The surface of the n-type contact layer 43 was exposed. The etching shape was a stripe shape parallel to the direction of the resonator to be formed later, and the stripe width was 10 μm.
[0039]
Next, a selective mesa etch is also performed on the p-type contact layer 51 by RIE, and the p-type contact layer 51, the p-type optical confinement layer 50, the p-type optical guide layer 49, and a part of the p-type layer 48 are striped. Was etched. The stripe width of the uppermost p-type contact layer remaining after etching was 1 μm, and the stripe width of the p-type layer 48 at the bottom of the trapezoid was about 4 μm.
[0040]
A mask is applied to the portions of the nitride semiconductor wafer on which the positive electrode and the negative electrode are to be formed after the etching, and the insulating film 11 made of SiO2 is further formed by a plasma CVD apparatus on the p-type contact layer 51, the p-type optical confinement layer 50, The light guide layer 49 and the p-type cap layer 48 were formed at a thickness of 4 μm on the etched end faces.
[0041]
Next, a stripe-shaped positive electrode 31 made of Ni and Au is formed on the p-type contact layer 51 via the insulating film 11, and a stripe-shaped stripe made of Ti and Al is formed on the previously exposed n-type contact layer 43. Of the negative electrode 21 was formed.
[0042]
The wafer as described above was first divided at a position parallel to the stripe-shaped electrodes, then divided in a direction perpendicular to the electrodes, and the divided surfaces divided in the vertical direction were polished to mirror surfaces. A dielectric multilayer film was formed on the resonance surface according to a conventional method to obtain a laser chip. This laser chip was placed on a heat sink and pulsed at room temperature. As a result, a laser oscillation of 410 nm was shown at a threshold current density of 2 kA / cm2.
[0043]
On the other hand, a 1 μm-wide current confinement layer made of SiO 2 (the exposed p-type contact layer has a stripe width of 1 μm) is provided on the surface of the p-type contact layer 51 without performing the mesa etching. The gain guided laser device provided with the electrodes had a threshold current density of 4 kA / cm 2 or more.
[0044]
【The invention's effect】
As described above, in the laser element formed by the forming method of the present invention, the laser current in the transverse mode can be controlled, so that the threshold current density of laser oscillation is reduced and it becomes possible to approach continuous oscillation. Was. Nitride semiconductors have the advantage that they can oscillate at shorter wavelengths than laser devices made of II-VI group compound semiconductors currently being studied. Therefore, if continuous oscillation is possible with a nitride semiconductor, the demand as a writing light source and a reading light source will explosively increase, and its industrial utility value will be very large.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing the structure of a laser device according to one embodiment of the present invention.
FIG. 2 is a perspective view showing the shape of the laser device of FIG. 1;
FIG. 3 is a schematic sectional view showing the structure of a laser device according to another embodiment of the present invention.
FIG. 4 is a schematic cross-sectional view showing the structure of a laser device according to another embodiment of the present invention.
[Explanation of symbols]
1 .... substrate
2 .... n-type contact layer
3 .... n-type optical confinement layer
4 .... n-type light guide layer
5 Active layer
6... P-type light guide layer
5 ... p-type optical confinement layer
6... P-type contact layer
10 Insulating thin film
20, 30, ... electrodes

Claims (5)

At least a p-type cap layer , a p-type light guide layer, a p-type light confinement layer, and a p-type contact layer in contact with the In-containing nitride semiconductor layer of the active layer are provided on the active layer made of the nitride semiconductor containing In. A method of manufacturing an effective refractive index type nitride semiconductor laser device,
The p-type cap layer is made of a p-type nitride semiconductor layer containing Al,
The p-type light guide layer is made of a nitride semiconductor containing p-type In or GaN,
The p-type optical confinement layer is made of a p-type nitride semiconductor containing Al.
The p-type contact layer is made of p-type InGaN or GaN,
The width of the p-type nitride semiconductor layer in a direction parallel to the resonance direction of the nitride semiconductor laser device is smaller than the width of the active layer and at a depth not exceeding the active layer. A method of etching the nitride semiconductor laser device so that at least a part of the nitride semiconductor laser device remains. The cross-sectional shape of the etched p-type nitride semiconductor layer includes a step of etching into a trapezoid with the active layer side at the bottom and the contact layer side at the top in a direction perpendicular to the laser light resonance direction. 2. The method for manufacturing a nitride semiconductor laser device according to item 1. 3. The method of manufacturing a nitride semiconductor laser device according to claim 1, wherein said p-type cap layer is doped with Mg. 4. The method for manufacturing a nitride semiconductor laser device according to claim 1, wherein said p-type cap layer has a thickness of 10 Å or more and 1 μm or less. 4. The method for manufacturing a nitride semiconductor laser device according to claim 1, wherein said p-type cap layer has a thickness of not less than 100 Å and not more than 0.1 μm.

Images