JP2002124737A - Nitride semiconductor laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor laser element which can obtain a stable perpendicular fundamental lateral mode and can reduce threshold current. SOLUTION: A semiconductor laser element 100 is formed by stacking a p-GaN buffer layer 2 doped with Mg, a p-InGaN crack protection layer 3 made of InGaN doped with Mg, a p-ALGaN clad layer 4 made of AlGaN doped with Mg, a light-emitting layer 5, an n-AlGaN clad layer 6 made of AlGaN doped with Si, and an n-GaN contact layer 7 made of GaN doped with Si on a p-GaN substrate 1 made of GaN doped with Mg. In the semiconductor laser element 100, the p-GaN substrate 1 and the layers 2 to 4 can absorb light leaked from the light-emitting layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a III-V semiconductor such as BN (boron nitride), GaN (gallium nitride), AlN (aluminum nitride), InN (indium nitride), TIN (thallium nitride) or a mixed crystal thereof. The present invention relates to a nitride semiconductor laser device made of a group III nitride semiconductor (hereinafter, referred to as a nitride semiconductor).

[0002]

2. Description of the Related Art In recent years, as a recording or reproducing light source used in a high-density and large-capacity optical disk system, research and development of a nitride-based semiconductor laser device emitting blue or violet light have been conducted.

FIG. 11 is a schematic sectional view showing an example of a conventional nitride semiconductor laser device. In the semiconductor laser device shown in FIG. 11, a buffer layer 82 made of undoped AlGaN is formed on a C (0001) plane of a sapphire substrate 81 by MOCVD (metal organic chemical vapor deposition).
Undoped GaN layer 83, n-Ga made of n-GaN
N contact layer 84, crack preventing layer 85 made of n-InGaN, n-AlGaN clad layer 86 made of n-AlGaN, light emitting layer 87 made of InGaN, p-A
A p-AlGaN cladding layer 91 made of 1GaN and a p-GaN contact layer 92 made of p-GaN are sequentially formed.

[0004] The light emitting layer 87 is made of n-G
aN optical guide layer 88, MQW active layer 89 made of InGaN and having a multiple quantum well (MQW) structure, and p-G
A p-GaN optical guide layer 90 made of aN is sequentially laminated.

[0005] From the p-GaN contact layer 92, p-Al
A predetermined depth of the GaN cladding layer 91 has been removed by etching. Thereby, a stripe-shaped ridge portion 93 composed of the p-GaN contact layer 92 and the p-AlGaN cladding layer 91 is formed, and the p-GaN contact layer 92 and the p-AlGaN cladding layer 91 are formed.
A flat portion is formed in the AlGaN cladding layer 91. A p-electrode 131 is formed on the p-GaN contact layer 92 of the ridge 93. Further, a part of the region from the flat portion of the p-AlGaN cladding layer 91 to the n-GaN contact layer 84 is removed by etching, and the n-electrode formation region 94 of the n-GaN contact layer 84 is exposed.
An n-electrode 132 is formed on the exposed n-electrode formation region 94.

[0006] Both sides of the ridge portion 93, p-AlGaN
Upper surface of the flat portion of the lad layer 91, p-AlGaN cladding layer
From 91 to the n-GaN contact layer 84,
N-GaN core excluding the region where the n-electrode 132 is formed
SiO on the contact layer 84 _Two Consisting of Si oxide such as
An insulating film 95 is formed.

[0007]

In the semiconductor laser device shown in FIG. 11, for example, the light emitting layer 87 and the n-AlGaN cladding layer 86 and the p-AlGaN cladding layer 91 are different from the conventional AlGaAs semiconductor laser device. The difference in refractive index is as small as about 1/4 to 1/3. For this reason,
The light generated in the MQW active layer 89 of the light emitting layer 87 is
It is hard to be guided by the light emitting layer 87.

Further, n-GaN contact layer 84 and p-GaN contact layer 92 located outside n-AlGaN cladding layer 86 and p-AlGaN cladding layer 91 for confining light generated in MQW active layer 89 of light emitting layer 87. Has a refractive index of n-AlGaN cladding layer 8
6 and a so-called anti-waveguide structure that is larger than the p-AlGaN cladding layer 91. Therefore, n-AlGa
N cladding layer 86 and p-AlGaN cladding layer 91
Light leaks into the n-GaN contact layer 84 and the p-GaN contact layer 92.

Here, for example, in the case of a conventional AlGaAs-based semiconductor laser device, a contact layer made of a material having a large absorption coefficient, such as GaAs, which absorbs laser light generated from an active layer made of AlGaAs. Can absorb light leaked from the cladding layer. However, since the n-GaN contact layer 84 and the p-GaN contact layer 92 made of GaN as described above have small absorption coefficients, the n-AlG
aN cladding layer 86 and p-AlGaN cladding layer 9
1 cannot absorb light oozing out.

From the above, in the above-described semiconductor laser device, it is difficult to sufficiently guide the light to the light emitting layer 87, the vertical transverse mode tends to become a higher-order mode, and a stable vertical fundamental transverse mode is obtained. Is difficult to obtain.

Particularly, in this case, the p-type layer 91,
Layer 8 on the sapphire substrate 81 side, which is thicker than 92
In 2 to 86 and the sapphire substrate 81, leakage of light becomes larger. Therefore, the sapphire substrate 81
On the side, the vertical and transverse modes are more likely to become higher-order modes.

As described above, in the above-described semiconductor laser device, it is difficult to obtain a stable vertical fundamental transverse mode, and thus it is difficult to reduce the threshold current.

On the other hand, as a method of preventing the vertical transverse mode from becoming a higher-order mode and obtaining a stable vertical fundamental transverse mode, an n-AlGaN cladding layer 86 and a p-AlGa
The Al composition of the N cladding layer 91 is increased (for example, 0.
07, or add a few% of Al to the n-GaN contact layer 84 (for example, 0.02
Degree). According to such a method, the vertical fundamental transverse mode is easily obtained in the semiconductor laser device.

However, in these cases,
By increasing the Al composition, cracks are likely to occur in the growth layer, and as a result, the yield of the device is greatly reduced.

By the way, the MQ of the above semiconductor laser device
The W active layer 89 is made of InGaN having a larger lattice constant than GaN or AlGaN. Such InG
The crystallinity of the MQW active layer 89 made of aN deteriorates as the film thickness increases. Therefore, the MQW active layer 8
In order not to deteriorate the crystallinity of the MQW 9, the MQW active layer 89
Needs to be reduced to several tens of millimeters.

However, the MQW active layer 8
In the case where the thickness of the layer 9 is reduced, light is not particularly guided to the light emitting layer 87, and the vertical transverse mode is more likely to be a higher mode. For this reason, it becomes more difficult to reduce the threshold current in the semiconductor laser device.

An object of the present invention is to provide a nitride-based semiconductor laser device capable of obtaining a stable vertical fundamental transverse mode and reducing the threshold current.

[0018]

Means for Solving the Problems and Effects of the Invention A nitride-based semiconductor laser device according to a first aspect of the invention has a structure in which a nitride-based semiconductor layer including an active layer is formed on a substrate. Wherein the substrate is made of a material capable of absorbing light leaked from the active layer.

In the nitride-based semiconductor laser device according to the present invention, since a substrate made of a material capable of absorbing the light leaked from the active layer is used, the light leaked from the active layer is applied to the substrate. It is possible to absorb.
Therefore, in such a nitride-based semiconductor laser device, it is possible to reduce light leakage from the active layer, and to prevent the vertical / lateral mode from becoming a higher-order mode.

As a result, in the above-described semiconductor laser device, a stable vertical fundamental transverse mode can be obtained, and the threshold current can be reduced.

In such a nitride-based semiconductor laser device, the vertical fundamental transverse mode can be realized without causing cracks in the nitride-based semiconductor layer. It becomes feasible.

The substrate may be made of a nitride-based semiconductor doped with magnesium. In a substrate composed of a nitride-based semiconductor doped with magnesium, light leaked from the active layer can be absorbed.

Further, the substrate may be composed of GaN doped with magnesium. In such a substrate, light leaked from the active layer can be absorbed.

At least a part of the substrate may be made of a nitride semiconductor having a band gap smaller than that of the active layer. In such a substrate, light leaked from the active layer can be absorbed in a portion composed of a nitride-based semiconductor having a smaller band gap than the active layer.

In the case where the active layer has a multiple quantum structure (MQW structure) composed of a barrier layer and a well layer, the band gap of the well layer is defined as the band gap of the active layer.

The active layer is composed of a nitride semiconductor containing InGaN, and at least a part of the substrate is made of InGa.
It may be composed of a nitride-based semiconductor containing N. In such a substrate, light leaked from the active layer is converted into InG.
It becomes possible to absorb in the portion composed of aN.

Further, the substrate may have a super lattice structure in which an InGaN layer and an AlGaN layer are laminated. In such a substrate, light leaked from the active layer is applied to InGaN.
It becomes possible to absorb in the layer, and it is possible to alleviate the strain generated between the substrate and the nitride-based semiconductor layer.

According to a second aspect of the present invention, there is provided a nitride-based semiconductor laser device having a first nitride-based semiconductor layer and a second nitride-based semiconductor layer including an active layer formed on a substrate. In the object-based semiconductor laser device, the first nitride-based semiconductor layer is made of a material capable of absorbing light leaked from the active layer.

In the nitride semiconductor laser device according to the present invention, the first nitride semiconductor layer is made of a material capable of absorbing light leaked from the active layer. Therefore, light leaked from the active layer can be absorbed in the first nitride-based semiconductor layer. Therefore, in such a nitride-based semiconductor laser device, it is possible to reduce light leakage from the active layer, and to prevent the vertical / lateral mode from becoming a higher-order mode.

As a result, in the nitride semiconductor laser device described above, a stable vertical fundamental transverse mode can be obtained, and the threshold current can be reduced.

In such a nitride-based semiconductor laser device, the vertical fundamental transverse mode can be realized without causing cracks in the nitride-based semiconductor layer. It becomes feasible.

[0032] The first nitride-based semiconductor layer may include a nitride-based semiconductor layer doped with magnesium. In such a first nitride-based semiconductor layer, light leaked from the active layer can be absorbed by the magnesium-doped nitride-based semiconductor layer.

The first nitride-based semiconductor layer is made of GaN, AlGaN or InGa doped with magnesium.
It may include a layer composed of N. In such a first nitride-based semiconductor layer, light leaked from the active layer can be absorbed in a layer made of GaN, AlGaN, or InGaN doped with magnesium.

The first nitride semiconductor layer may include a layer composed of a nitride semiconductor having a smaller band gap than the active layer. In such a first nitride-based semiconductor layer, light leaked from the active layer can be absorbed by a layer composed of the nitride-based semiconductor having a smaller band gap than the active layer.

In the case where the active layer has a multiple quantum structure (MQW structure) composed of a barrier layer and a well layer, the band gap of the well layer is defined as the band gap of the active layer.

The active layer is made of a nitride semiconductor containing InGaN, and the first nitride semiconductor layer is made of InG.
An aN layer may be included. In such a first nitride-based semiconductor layer, light leaked from the active layer is reflected by InGaN.
It becomes possible to absorb in the layer.

The first nitride-based semiconductor layer is made of InGa
It may include a superlattice structure in which an N layer and an AlGaN layer are stacked. In such a first nitride-based semiconductor layer, light leaked from the active layer can be absorbed in the InGaN layer.

[0038]

FIG. 1 is a schematic sectional view showing an example of a nitride-based semiconductor laser device according to the present invention. FIG.
Is manufactured by the following method.

At the time of manufacturing the semiconductor laser device 100
First, a thickness of 1 doped with Mg but made of GaN
An MOCVD method (organic) is formed on a 50 μm p-GaN substrate 1.
G doped with Mg by metal-chemical vapor deposition
aN 2 μm thick p-GaN buffer layer 2, M
g doped In_0.03Ga_0.97N thickness 0.
1 μm p-InGaN crack prevention layer 3, Mg
Al_0.07Ga _0.931.0 μm thick N
The p-AlGaN cladding layer 4, a light-emitting layer 5 described later, and Si
Doped Al_0.07Ga_0.930.4μ thick made of N
m n-AlGaN cladding layer 6 and Si doped
0.1 μm thick n-GaN contour made of GaN
Are grown in order.

In this case, as shown in FIG. 2, during the growth of the light emitting layer 5, first, a p-GaN light guide layer 51 of 0.1 μm thick made of Mg-doped GaN and Mg-doped. the Al _0.2 Ga p-AlGaN carrier block layer 52 having a thickness of 200Å formed of _0.8 N was grown in this order.

Subsequently, the p-AlGaN carrier block
On the layer 52, Si-doped In_0.02Ga_0.98N
N-InGaN barrier layer 53 and Si doped
In _0.09Ga_0.91N-InGaN well layer 54 made of N
Are alternately stacked to form a multiple quantum well structure (MQW structure).
The MQW active layer 57 having the same is grown.

In this case, in this case, the thickness is 100 mm.
Are stacked alternately with three n-InGaN barrier layers 53 of 50 .ANG.
A W active layer 57 is formed.

The MQW active layer 5 formed as described above
N-AlGaN carrier blocking layer 55 made of Al _0.2 Ga _0.8 N doped with Si and having a thickness of 200 °
Is further grown on the n-AlGaN carrier block layer 55, and an n-GaN optical guide layer 56 made of GaN doped with Si and having a thickness of 0.1 μm is grown.

As described above, the p-GaN light guide layer 51, the p-AlGaN carrier block layer 52, the MQW
Light emitting layer 5 composed of active layer 57, n-AlGaN carrier block layer 55 and n-GaN optical guide layer 56
To form

As described above, when manufacturing the semiconductor laser device 100, the Mg-doped p-GaN substrate 1 is used, and the Mg-doped p-GaN buffer layer is formed on the p-GaN substrate 1. 2, p-InGaN
The crack prevention layer 3 and the p-AlGaN cladding layer 4 are grown.

Here, usually, the layer and the substrate composed of the nitride-based semiconductor appear transparent to the naked eye, but the p-GaN substrate 1 and the substrate composed of the nitride-based semiconductor doped with Mg as described above. Each of the layers 2 to 4 is blackened by Mg. Thus, the p-GaN substrate 1, the p-GaN buffer layer 2, and the p-GaN
The InGaN crack prevention layer 3 and the p-AlGaN cladding layer 4 can absorb visible light.

It is to be noted that light can be absorbed in the p-GaN substrate 1 doped with Mg and each of the layers 2 to 4 as described above by doping Mg.
It is considered that impurity levels are formed in the energy bands of the p-GaN substrate 1 and the layers 2 to 4.

After the layers 2 to 7 are grown on the p-GaN substrate 1 as described above, the portions from the n-GaN contact layer 7 to the predetermined depth of the n-AlGaN cladding layer 6 are removed by etching. Thereby, a stripe-shaped ridge portion having a width of 2 μm constituted by the n-GaN contact layer 7 and the n-AlGaN cladding layer 6 is formed, and a flat portion having a thickness of 0.05 μm is formed on the n-AlGaN cladding layer 6. I do.

Next, a p-electrode 16 is formed by forming a Ni film on the surface of the p-GaN substrate 1 opposite to the crystal growth surface. Further, an insulating film 8 made of SiO _{2 having} a thickness of 0.3 μm is formed on the side surface of the ridge portion and the upper surface of the flat portion of the n-AlGaN cladding layer 6, and a Ti film and an Al film are formed on the upper surface of the ridge portion and the insulating film 8. The n-electrodes 15 are formed by stacking in order.

Finally, the cavity length 50
A resonator of 0 μm is manufactured. The semiconductor laser device 100 is manufactured as described above.

FIG. 3 is a schematic diagram showing the refractive indexes of the layers 2 to 7 and the p-GaN substrate 1 of the semiconductor laser device 100 manufactured by the above method.

The opposite relationship holds between the refractive indexes of the substrate and each layer and the width of the energy band gap of each of the substrate and each layer. That is, as the refractive index increases, the width of the energy band gap decreases. As the refractive index decreases, the width of the energy band gap increases.

As shown in FIG. 3, the semiconductor laser device 10
0, the refractive index of the MQW active layer 57 and p-AlG
The difference from the refractive index of the aN cladding layer 4 is small. For this reason,
It is difficult to sufficiently guide light generated in the MQW active layer 57 of the light emitting layer 5 into the light emitting layer 5, and light leaks from the light emitting layer 5 to the p-AlGaN cladding layer 4.

Here, the n-InGaN barrier layer 5
The average refractive index weighted by the thicknesses of the 3 and n-InGaN well layers 54 is defined as the refractive index of the MQW active layer 57.

The semiconductor laser device 100 has a p-A
The p-GaN buffer layer 2 located outside the lGaN cladding layer 4 has a so-called anti-waveguide structure having a larger refractive index than the p-AlGaN cladding layer 4. For this reason,
Light leaks from the p-AlGaN cladding layer 4 to the p-GaN buffer layer 2.

In particular, in the semiconductor laser device 100, since the thicknesses of the layers 2 to 4 on the p-GaN substrate 1 side below the light emitting layer 5 and the p-GaN substrate 1 are large, light is not Leakage increases.

Here, in the semiconductor laser device 100, as described above, the p-GaN substrate 1, the p-GaN buffer layer 2, the p-InGaN crack preventing layer 3, and the p-GaN
The AlGaN cladding layer 4 is doped with Mg,
The GaN substrate 1 and each of the layers 2 to 4 can absorb visible light. For this reason, the p-Ga
The light leaked to the N substrate 1 side is transmitted to the p-GaN substrate 1, p-G
It becomes possible to absorb in the aN buffer layer 2, the p-InGaN crack preventing layer 3, and the p-AlGaN cladding layer 4.

As described above, in the semiconductor laser device 100, the light leaked from the light emitting layer 5 to the p-GaN substrate 1 side is reflected by the p-GaN substrate 1, the p-GaN buffer layer 2, and the p-GaN buffer layer 2.
Since the light can be absorbed in the InGaN crack prevention layer 3 and the p-AlGaN cladding layer 4, light leakage from the light emitting layer 5 can be reduced, and the vertical transverse mode can be prevented from becoming a higher-order mode. It is possible to do. Thus, in the semiconductor laser device 100, a stable vertical fundamental transverse mode can be obtained, and the threshold current can be reduced.

As described above, in this case, p-
The Al composition of the AlGaN cladding layer 4 is increased (for example, larger than 0.07) or Al is added to the p-GaN buffer layer 2 (for example, Al is added to about 0.02).
Since the vertical basic transverse mode can be realized without causing the occurrence of cracks in the layers 2 to 7, it is possible to prevent the occurrence of cracks. Therefore, in the semiconductor laser device 100, manufacturing at a high yield can be realized.

In this case, the p-GaN substrate 1, p-GaN
GaN buffer layer 2, p-InGaN crack prevention layer 3
The light absorption in the p-AlGaN cladding layer 4 may not be so strong. Normally, the light absorption coefficient when light is absorbed is several thousands cm ⁻¹ , whereas the light absorption coefficient in the p-GaN substrate 1 and the entire layers 2 to 4 is several tens cm ⁻¹ or more. Good. Thus, even in the p-GaN substrate 1 and each of the layers 2 to 4 having a small light absorption coefficient, light can be sufficiently absorbed, and a stable vertical fundamental transverse mode can be realized.

Incidentally, the p-GaN substrate 1, the p-GaN buffer layer 2, the p-InGaN crack preventing layer 3, and the p-GaN
The doping concentration of Mg required to obtain the light absorption effect in the AlGaN cladding layer 4 is 1 × 10 ¹⁸ to 1
× 10 ²¹ cm ^-3 .

By increasing the doping concentration of Mg in the p-GaN substrate 1 and each of the layers 2 to 4, light absorption in the p-GaN substrate 1 and each of the layers 2 to 4 can be further increased. However, when the light absorption is increased by increasing the doping concentration of Mg, the p-GaN substrate 1 and each of the layers 2 to
In No. 4, a problem may occur in crystallinity.

Since the p-GaN substrate 1 absorbs light generated from the MQW active layer 57, if the distance between the p-GaN substrate 1 and the MQW active layer 57 is small, the p-GaN substrate 1
The light absorption in the GaN substrate 1 increases, and the semiconductor laser device 1
The threshold value of 00 may be increased.

However, in the semiconductor laser device 100, the thickness of the p-AlGaN cladding layer 4 is 1 μm.
P-GaN substrate 1 and MQW active layer 5
7 can be sufficiently separated. Therefore, in the semiconductor laser device 100, it is possible to prevent the light guided to the light emitting layer 5 from being absorbed and to absorb the light leaked from the light emitting layer 5.

FIG. 4 is a schematic sectional view showing another example of the nitride-based semiconductor laser device according to the present invention. The semiconductor laser device 101 shown in FIG. 4 is manufactured by the following method.

At the time of manufacturing the semiconductor laser element 101, first, the C of the sapphire substrate 20 having a thickness of 350 μm is
On the (0001) plane, undoped Al _0.5 Ga _0.5 N
AlGaN buffer layer 21 having a thickness of 200 °, undoped GaN layer 22 having a thickness of 2 μm, p-GaN contact layer 23 having a thickness of 5 μm made of GaN doped with Mg, and In _0.03 Ga _0.97 N doped with Mg. A 0.1 μm-thick p-InGaN crack prevention layer 24,
P-A made of Mg-doped Al _0.07 Ga _0.93 N
lGaN clad layer 25, light emitting layer 26, 0.4 μm thick n-AlGa made of Si-doped AlGaN
An N-cladding layer 27 and an n-GaN contact layer 28 made of Si-doped GaN and having a thickness of 0.1 μm are sequentially grown.

The light emitting layer 2 of the semiconductor laser device 101
6 has the same structure as the light emitting layer 5 of the semiconductor laser device 100 shown in FIG.

As described above, when the semiconductor laser device 101 is manufactured, the sapphire substrate 2 under the light emitting layer 26 is formed.
On the 0 side, a p-GaN contact layer 2 doped with Mg
3, p-InGaN crack preventing layer 24 and p-Al
A GaN cladding layer 25 is grown.

Here, usually, the layer and the substrate made of the nitride-based semiconductor appear transparent to the naked eye, but the p-GaN contact layer 23 made of the nitride-based semiconductor doped with Mg as described above. , P-InGaN crack prevention layer 24 and p-AlGaN cladding layer 25
It has a black color due to g. Thus, the p-GaN contact layer 23 doped with Mg and having a black color, p-I
The nGaN crack prevention layer 24 and the p-AlGaN cladding layer 25 can absorb visible light.

It is to be noted that Mg-doped p-GaN contact layer 23, p-InGaN crack preventing layer 24, and p-AlGaN cladding layer 25 can absorb light as described above because Mg is doped with Mg. It is considered that the impurity levels are formed in the energy bands of these layers 23 to 25 by doping.

After the layers 21 to 28 are grown on the sapphire substrate 20 as described above, the portions from the n-GaN contact layer 28 to a predetermined depth of the n-AlGaN cladding layer 27 are removed by etching. Thereby, n-Ga
N contact layer 28 and n-AlGaN cladding layer 2
7, a 2 μm-wide stripe-shaped ridge portion is formed, and a flat portion having a thickness of 0.05 μm is formed in the n-AlGaN cladding layer 27.

Subsequently, a partial region from the flat portion of the n-AlGaN cladding layer 27 to the p-GaN contact layer 23 is removed by etching, and the p-GaN contact layer 2 is removed.
Expose 3

Next, a Ni film is formed on a predetermined region of the exposed p-GaN contact layer 23 to form a p-electrode 16. Further, the n-GaN contact layer 28 in the ridge portion
A Ti film and an Al film are sequentially stacked thereon to form an n-electrode 15.

After crystal growth and electrode formation as described above, the back surface of the sapphire substrate 20 is polished to a thickness of 150 to 200 μm.

Further, the side surface of the ridge portion, the upper surface of the flat portion of the n-AlGaN cladding layer 27, the side surface from the n-AlGaN cladding layer 27 to the p-GaN contact layer 23,
An insulating film 70 made of SiO ₂ and having a thickness of 0.3 μm is formed on the upper surface of the GaN contact layer 23 excluding the p-electrode formation region and the upper surface of a predetermined region of the p-electrode 16.

Finally, the cavity length 50
A resonator of 0 μm is manufactured. The semiconductor laser element 101 is manufactured as described above.

FIG. 5 is a schematic diagram showing the refractive index of each of the layers 21 to 28 of the semiconductor laser device 101 manufactured by the above method.

As shown in FIG. 5, the semiconductor laser device 10
In No. 1, the difference between the refractive index of the light emitting layer 26 and the refractive index of the p-AlGaN cladding layer 25 is small. For this reason, it is difficult to sufficiently guide the light generated in the MQW active layer 57 of the light emitting layer 26 into the light emitting layer 26, and
The light leaks out to the p-AlGaN cladding layer 25 from the.

The semiconductor laser device 101 has a p-A
The p-GaN contact layer 23 located outside the lGaN clad layer 25 has a so-called anti-waveguide structure having a larger refractive index than the p-AlGaN clad layer 25. For this reason, the p-GaN
Light leaks into the contact layer 24.

In particular, in the semiconductor laser device 101, the thickness of the layers 21 to 25 and the sapphire substrate 20 below the light emitting layer 26, that is, the thickness of the sapphire substrate 20 is large. Become.

Here, in the semiconductor laser device 101, as described above, the p-GaN contact layer 23 and the p-GaN
The InGaN crack preventing layer 24 and the p-AlGaN cladding layer 25 are doped with Mg, and the respective layers 23 to 2
In 5 it is possible to absorb visible light. Therefore, light leaked from the light emitting layer 26 to the sapphire substrate 20 can be absorbed by the p-GaN contact layer 23, the p-InGaN crack prevention layer 24, and the p-AlGaN cladding layer 25.

As described above, in the semiconductor laser device 101, the light leaked from the light emitting layer 26 to the sapphire substrate 20 side is reflected by the p-GaN contact layer 23 and the p-InGaN
Crack prevention layer 24 and p-AlGaN cladding layer 2
5, the light emitting layer 26 can be absorbed.
This makes it possible to reduce the leakage of light from the light source and prevent the vertical and horizontal modes from becoming higher-order modes. Thereby, in the semiconductor laser element 101,
A stable vertical basic transverse mode can be obtained, and a reduction in threshold current can be achieved.

As described above, in this case, p-
Realizing the vertical fundamental transverse mode without increasing the Al composition of the AlGaN cladding layer 25 (for example, increasing it to more than 0.07) or adding Al to the p-GaN contact layer 23 (for example, adding Al about 0.02). Can be. Therefore, in the semiconductor laser device 101, it is possible to prevent the occurrence of cracks in each of the layers 2 to 7. Therefore, the semiconductor laser device 100 can be manufactured at a high yield.

In this case, the p-GaN contact layer 23, the p-InGaN crack preventing layer 24 and the p-A
The light absorption in the 1GaN cladding layer 25 may not be so strong, and the p-GaN contact layer 23 and the p-In
The light absorption coefficient of the entire GaN crack preventing layer 24 and the p-AlGaN cladding layer 25 may be several tens cm ^-1 or more. Thus, p-Ga having a small light absorption coefficient
N contact layer 23, p-InGaN crack prevention layer 2
The 4 and p-AlGaN cladding layers 25 can also sufficiently absorb light, and can realize a stable vertical fundamental transverse mode.

The p-GaN contact layer 23, p-GaN
In each of the InGaN crack prevention layer 24 and the p-AlGaN cladding layer 25, the doping concentration of Mg necessary for obtaining the light absorption effect is 1 × 10 ¹⁸ to 1 × 1.
0 ²¹ cm ^-3 .

The p-GaN contact layer 23, p-InG
By increasing the doping concentration of Mg in the aN crack preventing layer 24 and the p-AlGaN cladding layer 25, it becomes possible to increase light absorption in each of the layers 23 to 25. However, in the case where the absorption of light is increased by increasing the doping concentration of Mg in this manner, there is a concern that Mg may cause a problem in crystallinity in each of the layers 23 to 25.

In the semiconductor laser device 101, the thickness of the p-GaN contact layer 23 is preferably large, for example, preferably 10 to 20 μm. In the p-GaN contact layer 23 having such a large thickness, particularly large amounts of light can be absorbed. Thereby, in the semiconductor laser element 101, it is possible to further prevent the vertical / lateral mode from becoming a higher-order mode.

FIG. 6 is a schematic sectional view showing still another example of the nitride-based semiconductor laser device according to the present invention. FIG.
Is manufactured by the following method.

When the semiconductor laser device 102 is manufactured, an n-AlGaN / n-InGaN superlattice substrate 31 is manufactured by alternately stacking a plurality of n-AlGaN layers and n-InGaN layers.

In manufacturing the n-AlGaN / n-InGaN superlattice substrate 31, first, a 200 ° thick AlGaN buffer layer made of undoped Al _0.5 Ga _0.5 N and an undoped 2 μm thick layer are formed on a sapphire substrate. G
aN layer is grown. And this undoped G
On the aN layer, a 50 ° thick n-InGaN layer made of In _0.12 Ga _0.88 N doped with Si and a 50 ° thick n-Al made of Al _0.1 Ga _0.9 N doped with Si.
A plurality of GaN layers are laminated as a pair, and the thickness is 150 μm.
Grow up to. Thus, n-AlGaN / n-
After forming an InGaN superlattice structure, the sapphire substrate, the AlGaN buffer layer and the undoped Ga are polished by polishing.
The N layer is removed. As described above, a 150 μm-thick n-AlGaN / n-InGaN superlattice substrate 31 is manufactured.

Here, in this case, n-AlG
n-InGaN of aN / n-InGaN superlattice substrate 31
The width of the band gap of the layer is determined by the n-I
The composition of the n-InGaN layer of the n-AlGaN / n-InGaN superlattice substrate 31 is set to be smaller than the band gap width of the nGaN well layer 62. Thereby, in the n-InGaN layer of the n-AlGaN / n-InGaN superlattice substrate 31, the n-AlGaN
It is possible to absorb the light leaked to the aN / n-InGaN super lattice substrate 31 side.

The n-AlGaN fabricated as described above
/ N-InGaN superlattice substrate 31, a 2 μm thick n-GaN buffer layer 32 made of Si-doped GaN, and a 0.1 μm thick n-GaN buffer layer made of Si-doped In _0.03 Ga _0.97 N InGaN crack prevention layer 33,
A 1.0 μm thick n-AlGaN cladding layer 34 made of Si-doped Al _0.07 Ga _0.93 N, a light emitting layer 35 described later, and a 0.4 μm thick p-layer made of Mg-doped Al _0.07 Ga _0.93 N A thickness of 0.1 μm made of AlGaN cladding layer 36 and Mg-doped GaN
Are sequentially grown.

In this case, as shown in FIG.
When growing, first, Si-doped GaN
An n-GaN optical guide layer 61 of 0.1 μm in thickness is grown. Subsequently, on the n-GaN optical guide layer 61,
N-I composed of In _0.02 Ga _0.98 N doped with Si
nGaN barrier layer 62 and In _0.09 Ga doped with Si
MQW having a multiple quantum well structure (MQW structure) in which n-InGaN well layers 63 made of _0.91 N are alternately stacked.
The active layer 66 is grown. Further, the MQW active layer 6
A p-AlGaN carrier blocking layer 6 of 200 ° thick made of Mg-doped Al _0.2 Ga _0.8 N
4 and a thickness of 0.1 made of Mg-doped GaN
A μm p-GaN optical guide layer 65 is sequentially grown.

In this case, in this case, the thickness is 100 mm.
Are stacked alternately with three n-InGaN barrier layers 62 of 50 .ANG.
A W active layer 66 is formed.

As described above, n-AlGaN / nI
After the layers 32 to 37 are grown on the nGaN superlattice substrate 31, the p-GaN
The cladding layer 36 is removed by etching up to a predetermined region depth. Thereby, the width 2 composed of the p-GaN contact layer 37 and the p-AlGaN cladding layer 36 is
μm stripe ridges are formed
Forming a flat part having a thickness of 0.05 μm on the AlGaN cladding layer 36;

Next, an n-electrode 15 is formed by sequentially laminating a Ti film and an Al film on the surface of the n-AlGaN / n-InGaN superlattice substrate 31 opposite to the crystal growth surface. Further, an insulating film 38 made of SiO _{2 having} a thickness of 0.3 μm is formed on the side surface of the ridge portion and the upper surface of the flat portion of the p-AlGaN cladding layer 6, and a Ni film is formed on the upper surface of the ridge portion and the insulating film 38. A p-electrode 16 is formed.

Finally, the cavity length 50
A resonator of 0 μm is manufactured. The semiconductor laser device 102 is manufactured as described above.

FIG. 8 shows the n-AlGaN / n-InGaN of the semiconductor laser device 102 manufactured by the above method.
It is a schematic diagram which shows the superlattice board | substrate 31 and the refractive index which each layer 32-37 has.

As shown in FIG. 8, the semiconductor laser device 10
2, the refractive index of the MQW active layer 66 and n-AlG
The difference from the refractive index of the aN cladding layer 34 is small. For this reason, it is difficult to sufficiently guide light generated in the MQW active layer 66 of the light emitting layer 35 into the light emitting layer 35, and light leaks from the light emitting layer 35 to the n-AlGaN cladding layer 4.

Here, the n-InGaN barrier layer 6
The average refractive index weighted by the thickness of the 2 and n-InGaN well layers 63 is defined as the refractive index of the MQW active layer 66.

The semiconductor laser device 102 has an n-A
The n-GaN buffer layer 32 located outside the lGaN cladding layer 34 has a so-called anti-waveguide structure having a larger refractive index than the n-AlGaN cladding layer 34. Therefore, light leaks from the n-AlGaN cladding layer 34 to the n-GaN buffer layer 32.

In particular, in the semiconductor laser device 102, the n-AlGaN / n-InGaN
Layers 32-34 on superlattice substrate 31 side and n-AlGaN
/ N-InGaN superlattice substrate 31 has a large thickness,
On the n-AlGaN / n-InGaN superlattice substrate 31 side, light leakage increases.

Here, in the semiconductor laser device 102, as described above, the width of the band gap of the n-InGaN layer of the n-AlGaN / n-InGaN superlattice substrate 31 is determined by the n-InGaN well layer 62 of the light emitting layer 35. Is absorbed by the n-AlGaN / n-InGaN superlattice substrate 31 from the light-emitting layer 35 to the n-AlGaN / n-InGaN superlattice substrate 31 side. Is possible.

As described above, in the semiconductor laser device 102, the light leaked from the light emitting layer 35 is reflected by the n-AlGaN
Since the / n-InGaN superlattice substrate 31 can absorb light, it is possible to reduce light leakage from the light emitting layer 35 and prevent the vertical transverse mode from becoming a higher-order mode. Becomes Thereby, in the semiconductor laser element 102, a stable vertical fundamental transverse mode can be obtained, and the threshold current can be reduced.

As described above, in this case, n-
Realizing the vertical fundamental transverse mode without increasing the Al composition of the AlGaN cladding layer 34 (for example, increasing it to more than 0.07) or adding Al to the n-GaN buffer layer 32 (for example, adding Al about 0.02). Can be. Therefore, each of the layers 32 to 3 of the semiconductor laser device 102 is
In 7, the occurrence of cracks can be prevented.

Furthermore, in this case, n-AlG
Since the aN / n-InGaN superlattice substrate 31 has a superlattice structure, the strain generated between the n-AlGaN / n-InGaN superlattice substrate 31 and each of the layers 32 to 37 is reduced. Therefore, in the semiconductor laser device 102,
Cracks can be prevented from occurring.

As described above, in the semiconductor laser element 102, it is possible to prevent the occurrence of cracks in each of the layers 32 to 37, so that it is possible to realize the semiconductor laser element 102 at a high yield. Become.

Light absorption in the n-AlGaN / n-InGaN superlattice substrate 31 may not be so strong.
The light absorption coefficient of the AlGaN / n-InGaN superlattice substrate 31 may be several tens cm ^-1 or more. Thus, n-AlGaN / n-InGa having a small light absorption coefficient
Also in the N superlattice substrate 31, it is possible to sufficiently absorb the light leaked from the light emitting layer 35, and it is possible to realize a stable vertical fundamental transverse mode.

In the n-AlGaN / n-InGaN superlattice substrate 31, when the In composition of the n-InGaN layer is increased, the width of the band gap of the n-InGaN layer becomes smaller. InGa
Light absorption in the N superlattice substrate 31 can be further increased. However, the n-InGaN In
As the composition increases, the crystallinity of n-InGaN deteriorates. Accordingly, in the case where the absorption of light is increased by increasing the composition of In as described above, n-AlGaN /
The n-InGaN superlattice substrate 31 may have a problem in crystallinity.

Incidentally, n-AlGaN / n-InGa
Since the N superlattice substrate 31 absorbs light generated from the MQW active layer 66, when the distance between the n-AlGaN / n-InGaN superlattice substrate 31 and the MQW active layer 66 is small, n-AlGaN / n- The light absorption in the InGaN superlattice substrate 31 may increase, and the threshold value of the semiconductor laser device 102 may increase.

However, in the semiconductor laser device 102, the thickness of the n-AlGaN cladding layer 34 is 1 μm.
m and n-AlGaN / n-InGaN
The superlattice substrate 31 and the MQW active layer 66 can be sufficiently separated. Therefore, in the semiconductor laser device 102, the light guided to the light emitting layer 35 is n-AlGaN / n
-Prevent absorption by the InGaN superlattice substrate 31;
The light leaked from the light emitting layer 35 is converted into n-AlGaN / n
-It becomes possible to absorb in the InGaN super lattice substrate 31.

In the above-described semiconductor laser element 102, n-AlGaN / n-InGaN is used for the purpose of absorbing light and reducing strain.
Although the superlattice substrate 31 is formed, if only the light absorption effect is intended, a substrate in which an n-InGaN layer is partially inserted, for example, an n-InG layer having a thickness of 0.2 μm or less is used.
What is necessary is just to form a substrate having a structure in which the aN layer exists at a certain interval.

Since the lattice constant of InGaN is large, if the thickness of the n-InGaN layer is larger than 0.2 μm, the crystallinity of the n-InGaN layer deteriorates. Therefore, n
-The thickness of the InGaN layer is preferably 0.2 µm or less.

For example, an n-GaN / n-InGaN super lattice structure or an n-GaN / n-InGaN / n-AlG
A substrate having an aN superlattice structure may be formed. Also,
The substrate may have a periodic structure other than the superlattice structure,
Alternatively, a structure other than the superlattice structure and the periodic structure may be used. Also in this case, since the substrate can absorb light leaked from the light emitting layer, a stable vertical fundamental transverse mode can be obtained.

Here, a superlattice structure is a laminated structure in which layers having a thickness of 100 ° or less are laminated at a period of 200 ° or less, and a laminated structure in which layers having thicknesses and periods in other ranges are laminated. The periodic structure is distinguished from the superlattice structure.

In the above-described semiconductor laser device 102, the case where an n-type superlattice substrate is formed and an n-type layer and a p-type layer are formed in this order on the substrate has been described. A superlattice substrate may be formed, and a p-type layer and an n-type layer may be formed on the substrate in this order.

FIG. 9 is a schematic sectional view showing still another example of the nitride-based semiconductor laser device according to the present invention. FIG.
Is manufactured by the following method.

At the time of manufacturing the semiconductor laser element 103, first, the C of the sapphire substrate 40 having a thickness of 350 μm is
On the (0001) plane, undoped Al _0.5 Ga _0.5 N
AlGaN buffer layer 41 having a thickness of 200 °, undoped GaN layer 42 having a thickness of 2 μm, and a 5 μm-thick layer formed of AlGaN and InGaN doped with Si, which will be described later.
m-n-AlGaN / n-InGaN superlattice buffer layer 43, 1 μm-thick n-GaN contact layer 44 of Si-doped GaN, Si-doped Al
N-AlGaN cladding layer 4 made of _0.07 Ga _0.93 N
5, light emitting layer 46, Mg-doped Al _0.07 Ga _0.93
P-AlGaN cladding layer 47 of 0.4 μm in thickness made of N and a thickness of 0.4 μm of GaN doped with Mg.
A 1 μm p-GaN contact layer 48 is grown sequentially.

The light emitting layer 4 of the semiconductor laser device 103
6 is a light emitting layer 35 of the semiconductor laser device 102 shown in FIG.
It has the same structure as.

Here, in this case, n-AlG
n-In of aN / n-InGaN superlattice buffer layer 43
The width of the band gap of the GaN layer depends on the n-I
The composition of the n-InGaN layer of the n-AlGaN / n-InGaN superlattice buffer layer 43 is set to be smaller than the band gap width of the nGaN well layer 62. Thus, light leaked from the light emitting layer 46 to the sapphire substrate 40 side can be absorbed by the n-InGaN layer of the n-AlGaN / n-InGaN superlattice buffer layer 43.

After the layers 41 to 48 are grown on the sapphire substrate 40 as described above, the p-GaN contact layer 48 to a predetermined depth of the p-AlGaN cladding layer 47 are removed by etching. Thereby, p-Ga
N contact layer 48 and p-AlGaN cladding layer 4
7 and a stripe-shaped ridge portion having a width of 2 μm and a flat portion having a thickness of 0.05 μm are formed in the p-AlGaN cladding layer 47.

Subsequently, a partial region from the flat portion of the p-AlGaN cladding layer 47 to the n-GaN contact layer 44 is removed by etching to remove the n-GaN contact layer 4.
Expose 4.

Next, an n-electrode 15 is formed by sequentially laminating a Ti film and an Al film on a predetermined region of the exposed n-GaN contact layer 44. Also, the p-GaN of the ridge portion
A p-electrode 16 is formed by forming a Ni film on the contact layer 48.

After the crystal growth and electrode formation as described above, the back surface of the sapphire substrate 40 is polished so that the sapphire substrate 40 has a thickness of 150 to 200 μm.

Further, the side surface of the ridge portion, the upper surface of the flat portion of the p-AlGaN cladding layer 47, the side surface from the p-AlGaN cladding layer 47 to the n-GaN contact layer 44,
An insulating film 70 made of SiO _{2 having} a thickness of 0.3 μm is formed on the upper surface of the GaN contact layer 44 excluding the n-electrode formation region and on the upper surface of a predetermined region of the n-electrode 15.

Finally, the cavity length 50
A resonator of 0 μm is manufactured. The semiconductor laser device 103 is manufactured as described above.

FIG. 10 is a schematic diagram showing the refractive index of each of the layers 41 to 48 of the semiconductor laser device 103 manufactured by the above method.

As shown in FIG. 10, the semiconductor laser device 1
03, the refractive index of the light emitting layer 46 and n-AlGaN
The difference from the refractive index of the cladding layer 45 is small. For this reason, it is difficult to sufficiently guide the light generated in the MQW active layer 66 of the light emitting layer 46 into the light emitting layer 46, and the light emitting layer 4
From 6, light leaks into the n-AlGaN cladding layer 45.

Further, the semiconductor laser element 103 has the n-A
The n-GaN contact layer 44 located outside the lGaN cladding layer 45 has a so-called anti-waveguide structure having a larger refractive index than the n-AlGaN cladding layer 45. For this reason, n-GaN
Light leaks into the contact layer 44.

In particular, in the semiconductor laser element 103, since the thickness of the sapphire substrate 40 side, that is, the layers 41 to 45 below the light emitting layer 46 and the sapphire substrate 40 is large, the leakage of light is large on the sapphire substrate 40 side. Become.

Here, in the semiconductor laser element 103, as described above, the width of the band gap of the n-InGaN layer of the n-AlGaN / n-InGaN superlattice buffer layer 43 is determined by the n-InGaN well layer of the light emitting layer 46. 62 is smaller than the band gap width of the light emitting layer 4.
6 leaks to the sapphire substrate 40 side by n-Al
It is possible to absorb in the GaN / n-InGaN super lattice buffer layer 43.

As described above, in the semiconductor laser device 103, the light leaked from the light emitting layer 46 is reflected by the n-AlGaN
Since the / n-InGaN superlattice buffer layer 43 can absorb light, it is possible to reduce light leakage from the light emitting layer 46 and prevent the vertical transverse mode from becoming a higher mode. It becomes possible. Thus, in the semiconductor laser element 103, a stable vertical fundamental lateral mode can be obtained, and a reduction in threshold current can be achieved.

As described above, in this case, n-
Realizing the vertical fundamental transverse mode without increasing the Al composition of the AlGaN cladding layer 45 (for example, increasing it to more than 0.07) or adding Al to the n-GaN contact layer 44 (for example, adding Al about 0.02). Can be. Therefore, each of the layers 41 to 4 of the semiconductor laser device 103 is
In 8, the occurrence of cracks can be prevented.

Furthermore, in this case, n-AlG
Since the aN / n-InGaN superlattice buffer layer 43 has a superlattice structure, distortion between the n-AlGaN / n-InGaN superlattice buffer layer 43 and each of the layers 41, 42, 45 to 48 is reduced. For this reason, in the semiconductor laser element 103, the occurrence of cracks can be prevented.

As described above, in the semiconductor laser device 102, it is possible to prevent the occurrence of cracks in each of the layers 41 to 48. Therefore, it is possible to realize the semiconductor laser device 103 with a high yield. Become.

The light absorption in the n-AlGaN / n-InGaN superlattice buffer layer 43 does not have to be very strong, and the light absorption coefficient in the n-AlGaN / n-InGaN superlattice buffer layer 43 is several tens cm ^-1. All that is required is the above. As described above, the n-AlGaN /
Also in the n-InGaN superlattice buffer layer 43, it is possible to sufficiently absorb the light leaked from the light emitting layer 46, and to realize a stable vertical fundamental transverse mode.

In the n-AlGaN / n-InGaN superlattice buffer layer 43, the n-InGaN layer
When the composition is increased, the width of the band gap of the n-InGaN layer becomes smaller, so that n-AlGaN / n-I
Light absorption in the nGaN superlattice buffer layer 43 can be further increased. However, n-In
As the In composition of GaN increases, the crystallinity of n-InGaN deteriorates. For this reason, in the case of increasing the light absorption by increasing the composition of In, the n-Al
The GaN / n-InGaN superlattice substrate 31 may have a problem in crystallinity.

In the above-described semiconductor laser device 103, the n-AlGaN / n-InGaN superlattice buffer layer 43 is formed for the purpose of absorbing light and relaxing strain. If only the absorption effect is intended, a buffer layer in which the n-InGaN layer is partially inserted, for example, n having a thickness of 0.2 μm or less
A buffer layer having a structure in which the InGaN layer exists at a certain interval may be formed.

Since InGaN has a large lattice constant, the crystallinity of the n-InGaN layer deteriorates when the thickness of the n-InGaN layer exceeds 0.2 μm. Therefore, n
-The thickness of the InGaN layer is preferably 0.2 µm or less.

For example, an n-GaN / n-InGaN super lattice structure or an n-GaN / n-InGaN / n-AlG
A buffer layer having an aN superlattice structure may be formed.
Further, the buffer layer may have a periodic structure other than the superlattice structure, or may have a structure other than the superlattice structure and the periodic structure. Also in this case, since the substrate can absorb light leaked from the light emitting layer,
It is possible to obtain a stable vertical basic transverse mode.

Here, a superlattice structure is a laminated structure in which layers having a thickness of 100 ° or less are laminated at a period of 200 ° or less, and a laminated structure in which layers having thicknesses and periods in other ranges are laminated. The periodic structure is distinguished from the superlattice structure.

Further, in the above-described semiconductor laser device 103, the case where the n-type layer and the p-type layer are formed in this order on the sapphire substrate has been described. They may be formed in this order.

The composition of each layer of the semiconductor laser devices 100 to 103 is not limited to the above, and each layer is
What is necessary is just to be comprised from the nitride semiconductor containing at least one of Ga, Al, In, B, and Tl.

Although the sapphire substrates 20 and 40 are used in the semiconductor laser elements 101 and 103, a Si substrate, a SiC substrate or the like may be used instead of the sapphire substrates 20 and 40.

In the above description, the case where the present invention is applied to a semiconductor laser device having a ridge waveguide structure has been described. However, the present invention can be applied to a semiconductor laser device having a self-aligned structure. is there.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a semiconductor laser device according to the present invention.

FIG. 2 is a schematic sectional view showing a structure of a light emitting layer of the semiconductor laser device of FIG.

FIG. 3 is a schematic diagram showing the refractive index of the substrate and each layer of the semiconductor laser device of FIG. 1;

FIG. 4 is a schematic sectional view showing another example of the semiconductor laser device according to the present invention.

FIG. 5 is a schematic view showing a refractive index of each layer of the semiconductor laser device of FIG.

FIG. 6 is a schematic sectional view showing still another example of the semiconductor laser device according to the present invention.

FIG. 7 is a schematic sectional view showing a structure of a light emitting layer of the semiconductor laser device of FIG.

8 is a schematic diagram showing the refractive index of the substrate and each layer of the semiconductor laser device of FIG.

FIG. 9 is a schematic sectional view showing still another example of the semiconductor laser device according to the present invention.

FIG. 10 is a schematic diagram showing a refractive index of each layer of the semiconductor laser device of FIG.

FIG. 11 is a schematic sectional view showing the structure of a conventional semiconductor laser device.

[Explanation of symbols]

 Reference Signs List 1 p-GaN substrate 2 p-GaN buffer layer 3,24,33 p-InGaN crack prevention layer 4,25,36,47 p-AlGaN cladding layer 5,26,35,46 light-emitting layer 6,27,34,45 n-AlGaN cladding layer 7,28,44 n-GaN contact layer 8,38,70 insulating film 15 n-electrode 16 p-electrode 20 sapphire substrate 21 AlGaN buffer layer 23,37,48 p-GaN contact layer 100-103 semiconductor laser element

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Kano 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. (reference) 5F073 AA45 AA51 AA55 AA74 CA07 CB05 CB07 DA05 EA18 EA23

Claims (12)

[Claims] 1. A nitride-based semiconductor laser device comprising a substrate and a nitride-based semiconductor layer including an active layer formed thereon,
The substrate according to claim 1, wherein the substrate is made of a material capable of absorbing light leaked from the active layer. 2. The nitride semiconductor laser device according to claim 1, wherein said substrate is made of a nitride semiconductor doped with magnesium. 3. The nitride-based semiconductor laser device according to claim 2, wherein said substrate is made of GaN doped with magnesium. 4. The nitride-based semiconductor laser device according to claim 1, wherein at least a part of said substrate is made of a nitride-based semiconductor having a band gap smaller than said active layer. 5. The active layer is made of a nitride semiconductor containing InGaN, and at least a part of the substrate is made of InGaN.
5. The nitride-based semiconductor laser device according to claim 4, comprising a nitride-based semiconductor containing GaN. 6. The nitride semiconductor laser device according to claim 5, wherein said substrate has a superlattice structure in which an InGaN layer and an AlGaN layer are stacked. 7. A first nitride-based semiconductor layer on a substrate,
A nitride-based semiconductor laser device comprising a second nitride-based semiconductor layer including an active layer, wherein the first nitride-based semiconductor layer is capable of absorbing light leaked from the active layer. A nitride-based semiconductor laser device comprising a material. 8. The nitride-based semiconductor laser device according to claim 7, wherein said first nitride-based semiconductor layer includes a magnesium-doped nitride-based semiconductor layer. 9. The first nitride-based semiconductor layer is made of GaN, AlGaN, or InGa doped with magnesium.
9. The nitride-based semiconductor laser device according to claim 8, comprising a layer composed of N. 10. The nitride-based semiconductor according to claim 7, wherein said first nitride-based semiconductor layer includes a layer made of a nitride-based semiconductor having a smaller band gap than said active layer. Laser element. 11. The nitride semiconductor laser device according to claim 10, wherein said active layer is made of a nitride semiconductor containing InGaN, and said first nitride semiconductor layer contains an InGaN layer. . 12. The first nitride-based semiconductor layer is made of InG
The nitride-based semiconductor laser device according to claim 11, comprising a superlattice structure in which an aN layer and an AlGaN layer are stacked.