JPH11233886A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium-nitride-based semiconductor laser element, which can decrease the threshold current more by suppressing the lateral dispersion of the carriers injected into an active layer. SOLUTION: In this device, the ridge-stripe structure including at least an n-type Alx Ga1-x N (0<x<=1) clad layer 104, an Iny Ga1-y N (0<=y<=1) active layer 105 and p-type Alx Ga1-x N clad layer 106 is formed on a substrate 101. Furthermore, on the entire surface of the substrate 101, an Mg-doped Alx Ga1-x N layer 107 and an Mg-doped GaN layer 108 are sequentially laminated. The Mg-doped Alx Ga1-x N layer 107 and the Mg-doped GaN layer 108 on the ridge-stripe structure become the p-type region of low resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser device comprising a gallium nitride compound semiconductor.

[0002]

2. Description of the Related Art FIG. 10 is a view showing a gallium nitride based semiconductor laser device disclosed in Japanese Patent Application Laid-Open No. 8-125275. The semiconductor laser device of FIG. 10 is an n-type α-SiC
The layer thickness is 2 to 2 on the a surface of the substrate 1 by using the MOCVD method.
N-type GaN layer 2 having a thickness of 4 μm, n-type AlGaN cladding layer 3 having a thickness of 0.8 to 1 μm, and I having a thickness of 300 to 600 °
nGaN active layer 4, p-type AlG having a layer thickness of 0.8 to 1 μm
aN clad layer 5, p-type G having a layer thickness of 0.2 to 0.6 μm
The aN layers 6 are sequentially laminated. And p-type Ga
On both sides of the N layer 6 except for the center of the surface, an insulating layer 7 made of SiO ₂ or SiN is formed in a stripe shape for current confinement, and Au is formed over the insulating layer 7 and the exposed surface of the p-type GaN layer 6. An electrode 8 is formed, and α-S
A Ni electrode 9 is formed on the lower surface of the iC substrate 1. In this semiconductor laser device, by applying a predetermined voltage between the Au electrode 8 and the Ni electrode 9, a laser beam is emitted in the direction of the arrow.

FIG. 11 is a view showing a semiconductor light emitting device disclosed in Japanese Patent Application Laid-Open No. 8-97468. The semiconductor light emitting device of FIG. 11 has an n-type GaN on a sapphire substrate 10.
A low-temperature buffer layer 11 of about 0.01 to 0.02 μm, a high-temperature buffer layer 12 of about 2 to 5 μm, a lower cladding layer 13 of about 0.1 to 0.3 μm of n-type AlGaN, n-type or p-type I
It is made of nGaN, has a lower band gap energy than the lower cladding layer 13, and has a large refractive index of 0.05 to
An active layer 14 having a thickness of about 0.1 μm, an upper cladding layer 15 having the same composition as the lower cladding layer 13 and having a p-type thickness of 0.1 to 0.3 μm, and a contact layer 16 are sequentially laminated.

The contact layer 16 has the same composition as the buffer layers 11 and 12 and is a low resistance layer of 0.3 to 2 μm.
And a p-type InGaN layer 20 of about 0.05 to 0.2 μm. And
A p-side electrode 17 is formed on the InGaN layer 20, and an n-side electrode 18 is formed on the n-type cladding layer 13 or the high-temperature buffer layer 12 which is exposed by etching a part of the semiconductor layer stacked as described above. Are provided to form a semiconductor laser chip.

According to this semiconductor laser device, at least a portion of the contact layer 16 which is in contact with the p-side electrode 17 is p-type.
Since it is formed of a semiconductor material having a smaller band gap energy than that of the p-type GaN, that is, a p-type InGaN layer, the influence of the surface state can be reduced and the contact resistance with the p-side electrode 17 is reduced. .

FIG. 12 is a view showing a gallium nitride-based compound semiconductor laser device disclosed in Japanese Patent Application Laid-Open No. Hei 8-97502. In the semiconductor laser device of FIG. 12, an n-type GaN buffer layer 22 is formed on a sapphire substrate 21 by 2 to 5 μm.
Lower cladding layer 23 of m-type and n-type AlGaN
Is about 0.1 to 0.3 μm, and the active layer 24 made of non-doped or n-type or p-type InGaN is 0.05 to 0.3 μm.
About 0.1 μm, the upper first cladding layer 25 made of p-type AlGaN is about 0.1 to 0.3 μm, the current blocking layer 26 made of n-type Si is about 0.2 to 0.5 μm,
The upper second cladding layer 27 made of GaN has a thickness of 0.5 to 2 μm.
m, the contact layer 28 made of p-type GaN is 0.3
Each layer is sequentially laminated with a thickness of about 2 μm, and the upper electrode 29 made of Au or the like is formed on the surface of the laminated body.
Are formed. In addition, the lower electrode 30 is formed by etching a part of the laminate to a position where the lower clad layer 23 or the buffer layer 22 is exposed from the surface. Further, the current blocking layer 26 is partially removed in a striped shape by etching and has an opening to form a current path for a current reaching the active layer 24.

In this semiconductor laser device, the current blocking layer 26 formed in the stripe groove for regulating the current injection region is made of a material that absorbs light generated in the active layer 24. Thereby, the active layer 24 also has a function of providing a refractive index difference in the lateral direction to form a refractive index waveguide structure.

[0008]

In the conventional gallium nitride based semiconductor laser device shown in FIG. 10, the current injected into the active layer is formed by forming a stripe-shaped opening in the insulating layer 7 formed on the surface of the laminated structure. Stenosis, and FIG.
In the conventional gallium nitride-based semiconductor laser device shown in FIG. 1, a part of the laminated structure is removed by etching from the surface to the middle of the p-type AlGaN upper cladding layer 15 through the p-type contact layer 16 to form a ridge stripe structure. The current is confined to the width of the ridge stripe structure and injected into the active layer 14 by the ridge stripe structure. In the conventional gallium nitride based semiconductor laser device shown in FIG. A current blocking layer 26 made of Si is formed so that the current is concentrated in the region of the opening width W.

As described above, in the conventional gallium nitride based semiconductor laser device, although the current is confined at the upper part of the InGaN active layer, the lateral diffusion of the carriers injected into the InGaN active layer is not suppressed. This is one of the causes for increasing the threshold carrier density, that is, the threshold current.

An object of the present invention is to provide a gallium nitride-based semiconductor laser device capable of suppressing lateral diffusion of carriers injected into an active layer and further reducing a threshold current.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, at least n substrates are provided on a substrate.
Al _x Ga ₁ -xN (0 <x ≦ 1) cladding layer, In _y Ga
A ridge stripe structure including a _1-y N (0 ≦ y ≦ 1) active layer and a p-type Al _x Ga _1-x N cladding layer is formed, and a Mg-doped Al _x Ga _1-x N layer is formed on the entire surface of the substrate. , Mg-doped GaN layer are sequentially stacked, and the Mg-doped Al _x Ga ₁ -xN layer and the Mg-doped GaN on the ridge stripe structure are formed.
It is characterized in that the layer is a low-resistance p-type region.

[0012] Further, the invention according to claim 2 provides the above-mentioned, on a substrate,
At least an n-type Al _x Ga _1-x N (0 <x ≦ 1) cladding layer, an In _y Ga _1-y N (0 ≦ y ≦ 1) active layer, and a p-type Al _x G
A ridge stripe structure including an a _1-x N cladding layer is formed by selective growth, and a Mg-doped Al _x Ga _1-x N layer and a Mg-doped GaN layer are sequentially stacked on the entire surface of the substrate, thereby forming a ridge stripe structure. Mg-doped Al on
_The xGa1 _-xN layer and the Mg-doped GaN layer are characterized by being low resistance p-type regions.

[0013] Further, the invention according to claim 3 is a method for manufacturing a semiconductor device, comprising:
At least an n-type Al _x Ga _1-x N (0 <x ≦ 1) cladding layer, an In _y Ga _1-y N (0 ≦ y ≦ 1) active layer, and Mg-doped A
A ridge stripe structure including an l _x Ga _1-x N cladding layer and a Mg-doped GaN contact layer is formed, and the side surface of the ridge stripe structure is Mg-doped Al _z Ga.
_1-z N (0 ≦ z <1) layer, almost flat buried with Mg-doped GaN layer, and In _y Ga _1-y N
Mg-doped GaN layer above active layer, Mg-doped A
l _x Ga _1-x N layer, Mg-doped Al _z Ga _1-z N layer is characterized in that it is a low-resistance p-type region.

[0014] Further, the invention according to claim 4 is the invention, wherein:
At least an n-type Al _x Ga _1-x N (0 <x ≦ 1) cladding layer, an In _y Ga _1-y N (0 ≦ y ≦ 1) active layer, and Mg-doped A
A trapezoidal or triangular ridge stripe structure including an l _x Ga _1-x N cladding layer is formed by selective growth, and the side surface of the ridge stripe structure is Mg-doped A.
1 _z Ga _{1 -zN} (0 ≦ z <1) layer, almost flat buried with Mg-doped GaN layer, and In _y G
Mg-doped GaN layer above a _1-y N active layer, Mg
It is characterized in that the doped Al _x Ga _{1 -x} N layer and the Mg doped Al _z Ga _{1 -z} N layer are p-type regions with low resistance.

[0015] The invention according to claim 5 is a device according to claim 5, wherein
At least a trapezoidal or triangular ridge stripe structure including an n-type Al _x Ga _1-x N (0 <x ≦ 1) cladding layer and an In _y Ga _1-y N (0 ≦ y ≦ 1) active layer is selected. The In _y Ga _1-y N (0 ≦ y ≦ 1) active layer is provided near the top of a trapezoidal or triangular ridge stripe structure, and the ridge stripe structure is formed of Mg-doped Al. _x Ga _1-x N layer and Mg-doped GaN layer are almost flatly buried, and the In _y G
a _1-y N active layer Mg doped GaN layer to the vicinity, Mg-doped Al _x Ga _1-x N layer is characterized in that it is a low-resistance p-type region.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first configuration example of a semiconductor laser device according to the present invention. Referring to FIG. 1, this semiconductor laser device includes at least an n-type Al _x Ga ₁ -xN (0 <x ≦ 1) cladding layer 10 on a substrate 101.
4, In _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105, p-type A
A ridge stripe structure including an l _x Ga _1-x N cladding layer 106 is formed, and a Mg-doped A
The l _x Ga _1-x N layer 107 and the Mg-doped GaN layer 108 are sequentially stacked, and the Mg-doped Al _x Ga _1-x N layer 107 and the Mg-doped GaN layer 108 on the ridge stripe structure are formed.
(A region 109 indicated by oblique lines in FIG. 1) is a low-resistance p-type region.

That is, in the configuration of FIG. 1, the n-type Al _x G
a _1-x N (0 <x ≦ 1) cladding layer 104, In _y Ga _1-y
A ridge stripe structure including an N (0 ≦ y ≦ 1) active layer 105 and a p-type Al _x Ga _1-x N cladding layer 106 is formed, and the In _y Ga _1-y N active layer 105 has a ridge stripe structure. The width is limited. Then, the side surface is buried with an Mg-doped Al _x Ga ₁ -xN layer 107.

In such a configuration, Al _x Ga ₁ -xN (0
<X ≦ 1) when the band gap energy is In _y Ga _1-y
N (0 ≦ y ≦ 1), so that In _y Ga _1-y N (0
_{≦ y ≦ 1) / Al x} Ga 1-x N (0 <x ≦ 1) interface hetero barrier by _{In y Ga 1-y N (} 0 ≦ y ≦ 1) active layer 105
(Power supply) injected into the ridge is narrowed to the ridge stripe width. Therefore, it is possible to effectively suppress the carrier (power supply) from being diffused in the horizontal direction.

In _y Ga _1-y N (0 ≦ y ≦ 1) is Al
_x Ga _1-x N so (0 <x ≦ 1) refractive index than is high material, the light in the refractive index difference _{In y Ga 1-y N (} 0 ≦ y ≦ 1)
The refractive index waveguide structure is confined in the active layer 105.

Further, when Mg-doped Al _x Ga ₁ -xN and Mg-doped GaN are grown by metal organic chemical vapor deposition using NH ₃ as a nitrogen source, the resistivity of the film remains unchanged. It is as high as 10 ⁴ Ω · cm or more. It is known that the cause is that Mg as an acceptor is inactivated by hydrogen taken into the film in an NH ₃ atmosphere. Therefore, FIG.
In the semiconductor laser device of FIG.
For the g-doped Al _x Ga ₁ -xN layer 107 and the Mg-doped GaN layer 108, hydrogen in these films is desorbed,
It is changed to a low resistance p-type. in this case,
The resistivity of the low-resistance p-type region is reduced to about several Ω · cm. On the other hand, the Mg-doped Al _x Ga ₁ -xN layer 107 and the Mg-doped GaN layer 108 on the side surfaces of the ridge stripe structure have not been desorbed from hydrogen and remain at high resistance. As a result, the current is concentrated on the ridge stripe having a low resistance, and carriers are injected into the In _y Ga _{1 -y} N (0 ≦ y ≦ 1) active layer 105.

The Mg-doped Al _x Ga ₁ -xN layer 107 and the Mg-doped GaN layer 108 on the ridge stripe structure
As a method for desorbing hydrogen therein, there is a method of directly irradiating the top of the ridge stripe structure with an electron beam without using a mask using an electron beam lithography apparatus. Also, the side surfaces of the ridge stripe structure are covered with a photoresist, polyimide, SOG, or the like by spin coating, and the entire substrate is irradiated with an electron beam to expose the Mg-doped Al _x Ga ₁ -xN layer 1 on the ridge stripe structure.
It is also possible to lower the resistance of only the 07, Mg-doped GaN layer 108. In addition, there is a method of irradiating the top of the ridge stripe structure with light having a wavelength shorter than the band gap wavelength of the Al _x Ga ₁ -xN layer 106.

The Mg-doped Al _x Ga ₁ -xN layer 10
7. The depth at which the electron beam penetrates the Mg-doped GaN layer 108 to reduce the resistance is about 0.5 μm. Therefore, the thickness from the In _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105 to the element surface needs to be 0.5 μm or less. For example, the thickness of the p-type Al _x Ga ₁ -xN cladding layer 106 having the ridge stripe structure is 0.1 μm, the thickness of the Mg-doped Al _x Ga ₁ -xN layer 107 as the burying layer is 0.3 μm,
By setting the layer thickness of the doped GaN layer 108 to 0.1 μm,
The semiconductor laser device of FIG. 1 can be configured.

More specifically, the semiconductor laser device shown in FIG. 1 has, for example, an AlN low-temperature buffer layer 102 and a Si-doped n-type GaN contact layer 1 on a sapphire substrate 101.
03 are sequentially stacked, and an n-type AlGaN cladding layer 104 and an InGaN-M
QW active layer 105, Mg-doped AlGaN cladding layer 1
06 are stacked to form an n-type AlGaN cladding layer 104,
InGaN-MQW active layer 105, Mg-doped AlGa
The N cladding layer 106 is formed as a ridge stripe structure. Further, Mg-doped AlGaN is formed on the n-type GaN contact layer 103 and the ridge stripe structure.
A layer 107 and a Mg-doped GaN layer 108 are sequentially stacked,
A ridge stripe structure is embedded.

In FIG. 1, a hatched portion 109 is formed, for example, by irradiating an electron beam with the Mg-doped GaN layer 10.
8, Mg-doped AlGaN layer 107, Mg-doped AlG
A part of the aN cladding layer 106 is a low resistance p-type region. Then, a p-side electrode 110 is formed on the surface of the Mg-doped GaN layer 108, and the n-type G
An n-side electrode 111 is formed on the n-type GaN contact layer 103 whose surface is exposed by being etched until reaching the aN contact layer 103.

FIG. 2 is a diagram showing an example of a manufacturing process of the semiconductor laser device of FIG. Referring to FIG. 2, first, FIG.
(a) As shown in FIG.
0 ° AlN low temperature buffer layer 102, 2 μm thick Si
Doped n-type GaN layer 103, 0.8 μm thick Si-doped n-type Al _0.1 Ga _0.9 N layer 104, non-doped InGa
An N-MQW active layer 105 and a Mg-doped Al _0.1 Ga _0.9 N layer 106 having a thickness of 0.1 μm are sequentially formed. In addition,
Metal-organic vapor phase epitaxy can be used for these crystal growth methods.

Next, as shown in FIG. 2B, a stripe-shaped Cr mask 201 having a width of 3 μm is formed on the Mg-doped Al _0.1 Ga _0.9 N layer 106 by a lift-off method.
Mg-doped Al _0.1 G using Cr mask 201 as a mask
From the surface of the a _0.9 N layer 106 to the n-type GaN contact layer 10
Then, dry etching is performed until the number reaches 3, and a ridge stripe structure 202 is formed.

Next, after removing the Cr mask 201,
0.3 μm layer thickness over the entire surface of the substrate by metal organic chemical vapor deposition
Mg-doped Al _0.1 Ga _0.9 N layer 107, layer thickness _0.1 μm
m-doped GaN layers 108 are sequentially stacked (FIG.
(c)).

Subsequently, a photoresist 203 is formed on the substrate surface.
Is spin-coated to flatten the substrate surface, and the photoresist 203 is etched by O ₂ plasma ashing until the top of the ridge stripe structure 202 is exposed. Then, by irradiating the entire substrate with, for example, an electron beam EB, the Mg-doped layer is changed to a low-resistance p-type to a depth of about 0.5 μm from the surface. At the top of the ridge stripe structure 202 where the surface is exposed, M
g-doped GaN layer 108, Mg-doped Al _0.1 Ga _0.9 N
Layer 107, Mg-doped Al _0.1 Ga _0.9 N clad layer 10
The p-type region 109 has a low resistance up to 6. On the other hand, outside the ridge stripe structure 202 (side surface), Mg-doped GaN
A photoresist 203 having a thickness of about 0.8 μm is formed on the surface of the layer 108.
m, the ridge stripe structure 20
2, Mg-doped GaN layer 108, Mg-doped Al
_{The 0.1} Ga _0.9 N layer 107 remains at a high resistance (FIG. 2D).

Next, after the photoresist 203 is removed, Mg-doped Ga is removed except for the region where the n-side electrode is to be formed.
P-side electrode 110 made of Ni / Au on the surface of N layer 108
And a Cr mask 204 are formed by vapor deposition (FIG. 2E).

Thereafter, dry etching is performed from the surface of the Mg-doped GaN layer 108 to the n-type GaN contact layer 103 using the Cr mask 204 as a mask.
Finally, n-type Ga whose surface is exposed by dry etching
An n-side electrode 111 made of Ti / Al is formed on the N contact layer 103 (FIG. 2F).

In the semiconductor laser device manufactured in the above-described steps, the InGaN-MQW active layer 105 is formed so that the width of the ridge stripe structure 202 is limited to 3 μm. Then, the side surface is made of Mg-doped Al _0.1 Ga _0.9
The structure is buried with the N layer 107. Al _0.1 G
Since the band gap energy of a _0.9 N is greater than InGaN, carriers injected into InGaN-MQW active layer 105 by the heterobarrier InGaN / Al _0.1 Ga _0.9 N interface is confined to a region of width 3 [mu] m. Therefore, the carrier is prevented from being diffused in the horizontal direction.

Further, since InGaN is a material having a higher refractive index than Al _0.1 Ga _0.9 N, it is possible to prevent the carriers from being diffused in the horizontal direction, and at the same time, to reduce the light due to the difference in refractive index.
The refractive index waveguide structure is confined in the nGaN-MQW active layer 105.

Further, the side surface of the ridge stripe structure 202 is flattened with a photoresist 203, and the top of the ridge stripe structure 202 is irradiated with, for example, an electron beam so as to have a depth of 0.5 μm from the top of the ridge stripe.
The Mg-doped layer up to about m becomes the p-type region 109 with low resistance. The low-resistance p-type region 109, Mg-doped GaN layer 108 having a thickness of 0.1 [mu] m, Mg-doped the Al _0.1 Ga _0.9 N layer, 107 having a thickness of 0.3 [mu] m, the layer thickness 0.1 [mu] m Mg-doped Al _0.1 Ga _0.9 N The cladding layer 106 is included.
On the other hand, the Mg-doped GaN layer 108 and the Mg-doped Al _0.1 Ga _{0.9 on} the outside (side surface) of the ridge stripe structure 202 covered with the photoresist 203 and not irradiated with the electron beam.
The N layer 107 has a very high resistivity of 10 ⁴ Ω · cm or more. Therefore, current flows intensively in the ridge stripe structure 202 having a low resistance, and carriers (current) are injected into the InGaN active layer 105.

That is, the Mg-doped Al _x Ga ₁ -xN layer 107 on the ridge stripe structure 202 and the Mg-doped Ga
The N layer 108 is a low-resistance p-type region, while the Mg-doped A
The resistivity of the l _x Ga _1-x N layer 107 and the Mg-doped GaN layer 108 is as high as 10 ⁴ Ω · cm or more, and the current is concentrated on the ridge stripe structure 202 having a low resistance and the InGaN active layer 105 Is injected into the carrier. In
The GaN active layer 105 is configured to be limited to the width of the ridge stripe structure 202, and has a structure in which the side surfaces are buried with the Mg-doped AlGaN layer 107, so that the carriers injected into the InGaN active layer 105 are heterogeneous. The barrier narrows the width of the ridge stripe, thereby suppressing the carrier from diffusing in the horizontal direction. Thereby, the threshold current of the element can be reduced.

As described above, in the structure of the semiconductor laser device shown in FIG.
Since the configuration is made to concentrate on the m ridge stripe structure, the threshold current of the laser can be reduced.

FIG. 3 is a diagram showing a second configuration example of the semiconductor laser device according to the present invention. In the semiconductor laser device of FIG. 3, at least n-type Al _x Ga ₁ -xN
(0 <x ≦ 1) cladding layer 104, In _y Ga _1-y N (0 ≦
y ≦ 1) A ridge stripe structure including an active layer 105 and a p-type Al _x Ga ₁ -xN cladding layer 106 is formed by selective growth, and further, Mg-doped Al _x G is formed on the entire surface of the substrate.
a _1-x N layer 107 and an Mg-doped GaN layer 108 are sequentially stacked, and Mg-doped A on the ridge stripe structure is formed.
The l _x Ga _1-x N layer 107 and the Mg-doped GaN layer 108 are low resistance p-type regions.

The semiconductor laser device of FIG. 3 is different from the semiconductor laser device of FIG. 1 in that n-type Al _x Ga ₁ -xN (0
<X ≦ 1) cladding layer 104, In _y Ga _1-y N (0 ≦ y ≦
1) active layer 105, p-type Al _x Ga _1-x N cladding layer 10
6 is that the ridge stripe structure including No. 6 is formed by selective growth. For example, as described below, SiO ₂
The film is stacked on the (0001) plane n-type GaN contact layer 103, and a stripe-shaped window is formed in the <11-20> direction to form a mask for selective growth. When a GaN-based material is grown, basically SiO ₂
A rectangular or trapezoidal ridge stripe structure can be formed on the surface where the n-type GaN contact layer 103 is exposed in a stripe shape without being crystallized on the film. At this time, the crystal growth slightly progresses in a direction horizontal to the substrate surface, that is, in a lateral direction, although the growth rate is lower than that in the case of growing in a direction perpendicular to the substrate surface.

When the ridge stripe structure is formed by dry etching as in the configuration examples shown in FIGS. 1 and 2, the side surface of the In _y Ga _{1 -yN} (0 ≦ y ≦ 1) active layer 105 is formed by dry etching. The ridge stripe structure is damaged or In _y Ga _1-y N (0 ≦ y ≦ 1)
Since the active layer 105 is exposed, Mg-doped Al _x G
The side surface of the In _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105 may be damaged by the heat treatment during the temperature rise for the embedded growth of the a _1-x N layer 107 and the Mg-doped GaN layer 108. There is.

On the other hand, when the ridge stripe structure is formed by selective growth as in the semiconductor laser device of FIG. 3, no etching damage occurs because dry etching is not used. Furthermore, the lateral surface of the In _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105 is buried with the Al _x Ga _1-x N (0 <x ≦ 1) cladding layer 106 by the lateral growth during the selective growth. Therefore, damage due to the heat treatment is reduced. Therefore, crystal defects on the side surface of the In _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105 are reduced, and the leakage current during operation can be reduced.

As described above, the semiconductor laser device of FIG.
n-type Al _x Ga ₁ -xN (0 <x ≦ 1) cladding layer 104, I
n _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105, Mg-doped A
The point that the ridge stripe structure formed by laminating the l _x Ga _1-x N (0 <x ≦ 1) cladding layer 106 is formed not by dry etching but by selective growth using a metal organic chemical vapor deposition method. Unlike the structure of the semiconductor laser device of FIG. 1, a semiconductor laser device having better and more reliable characteristics can be provided.

FIG. 4 is a view showing an example of a manufacturing process of the semiconductor laser device of FIG. Referring to FIG. 4, first, FIG.
As shown in FIG. 2A, an AlN low-temperature buffer layer 102 having a thickness of 200 ° and a Si-doped n-type GaN contact layer 103 having a thickness of 2 μm are sequentially stacked on a sapphire substrate (0001) surface 101 by metal organic chemical vapor deposition. Form. Next, n-type G
An SiO ₂ film 401 is formed on the aN contact layer 103. Then, using a photoresist as a mask, the SiO ₂ film 401 is removed by etching in a stripe shape in the <11-20> direction, and the n-type GaN is formed into a stripe shape having a width of 2 μm.
The contact layer 103 is exposed (FIG. 4B).

Next, using selective growth by metal organic chemical vapor deposition, a 0.8 μm thick Si-doped n-type Al
_0.1 Ga _0.9 N layer 104, non-doped InGaN-MQW
Active layer 105, Mg-doped Al _0.1 G having a thickness of 0.1 μm
An a _0.9 N layer 106 is sequentially laminated (FIG. 4C). At this time, by using selective growth, the SiO ₂ film 401 is formed.
A ridge stripe structure 202 is formed basically without crystal growth.

Next, after removing the SiO ₂ film 401,
0.3 μm layer thickness over the entire surface of the substrate by metal organic chemical vapor deposition
Mg-doped Al _0.1 Ga _0.9 N layer 107, layer thickness _0.1 μm
m-doped GaN layers 108 are sequentially stacked (FIG.
(d)).

Subsequently, a photoresist 203 is formed on the substrate surface.
Is spin-coated to flatten the substrate surface, and the photoresist 203 is etched by O ₂ plasma ashing until the top of the ridge stripe structure 202 is exposed. Then, by irradiating the entire substrate with, for example, an electron beam EB, the Mg-doped layer is changed to a low-resistance p-type to a depth of about 0.5 μm from the surface. At the top of the ridge stripe structure 202 where the surface is exposed, M
g-doped GaN layer 108, Mg-doped Al _0.1 Ga _0.9 N
Layer 107, Mg-doped Al _0.1 Ga _0.9 N clad layer 10
The p-type region 109 has a low resistance up to 6. On the other hand, outside the ridge stripe structure 202 (side surface), Mg-doped GaN
A photoresist 203 having a thickness of about 0.8 μm is formed on the surface of the layer 108.
m, the Mg-doped GaN layer 10
8. The Mg-doped Al _0.1 Ga _0.9 N layer 107 remains at a high resistance (FIG. 4E).

Finally, after removing the photoresist 203, a p-side electrode 110 made of Ni / Au is formed on the surface of the Mg-doped GaN layer 108, and the Mg-doped GaN layer is formed.
N-type GaN exposed by dry etching from the surface of layer 108 to n-type GaN contact layer 103
N-side electrode 1 made of Ti / Al on contact layer 103
11 is formed (FIG. 4F).

As described above, in the semiconductor laser device shown in FIGS. 3 and 4, the ridge stripe structure is formed by selective growth as shown in the above-described process. Unlike the manufacturing process shown in FIG. Since dry etching is not used in the formation, the ridge stripe structure 2
02 is not damaged by dry etching.

According to the selective growth, basically, SiO 2
_The crystal is not grown on ₂ but is grown in a rectangular or trapezoidal shape on the exposed surface of the n-type GaN buffer layer 103 in a stripe shape. Although the growth rate is slower, crystal growth slightly progresses in a direction parallel to the substrate surface, that is, in a lateral direction. Therefore, the side surface of the InGaN-MQW active layer 105 is buried by the Mg-doped Al _0.1 Ga _0.9 N layer 106, and the side surface of the InGaN-MQW active layer 105 is not exposed to the side surface of the ridge stripe structure. For this reason,
Mg-doped Al _0.1 Ga _0.9 N layer 107, Mg-doped Ga
At the time of raising the temperature for growing the N layer 108, In at a low growth temperature is used.
The GaN layer 105 can be prevented from being damaged by the heat treatment.

[0048] Thus, FIG. 3, the semiconductor laser device of FIG. 4, FIG. 1, in addition to the above-described effect of the semiconductor laser device of FIG. 2, since the ridge stripe structure is formed by selective growth, an In _y The side surface of the Ga _1-y N (0 ≦ y ≦ 1) active layer 105 is not damaged by dry etching or heat treatment, and In _y Ga _1-y N (0 ≦ y ≦ 1)
Crystal defects on the side surface of the active layer 105 are reduced, so that leakage current during device operation can be reduced.

FIG. 5 is a diagram showing a third configuration example of the semiconductor laser device according to the present invention. In the semiconductor laser device of FIG. 5, at least n-type Al _x Ga ₁ -xN
(0 <x ≦ 1) cladding layer 104, In _y Ga _1-y N (0 ≦
y ≦ 1) A ridge stripe structure including the active layer 105, the Mg-doped Al _x Ga ₁ -xN cladding layer 106, and the Mg-doped GaN contact layer 501 is formed.
, A Mg-doped GaN layer 501, a Mg-doped Al _x Ga ₁ -xN cladding layer 106 above the In _y Ga _{1 -y} N active layer 105 from the surface of the stacked structure, The GaN layer 502 is a low-resistance p-type region 109.

More specifically, in the semiconductor laser device of FIG. 5, a selective growth mask such as SiO ₂ is formed on the top of the ridge stripe structure, and the Mg-doped GaN layer 502 is grown only on the side surfaces of the ridge stripe structure. Thus, the ridge stripe structure is buried almost flat. And
For example, an electron beam EB is applied to the entire surface of the substantially flat laminated structure to irradiate the In _y Ga _1-y N active layer 105 from the surface of the laminated structure.
Mg-doped GaN layer 501, Mg-doped Al
_x Ga _1-x N layer 106, Mg-doped Al _z Ga _1-z N layer 50
2, a low-resistance p-type region is formed. Since in the ridge outer stripe structure _{(aspect) In y Ga 1-y N} (0 ≦ y ≦ 1) Mg -doped Al _z Ga _1-z N layer 502 than the active layer 105 side is located below the electron beam does not enter The current (carrier) remains at the high resistance, and the current (carrier) passes through the ridge stripe structure of the low resistance region and the In _y Ga _1-y N (0 ≦ y ≦ 1) active layer 105
Is injected into.

As described above, the semiconductor laser device of FIG.
Si-doped n-type Al _0.1 G formed by dry etching
a _0.9 N layer 104, non-doped InGaN-MQW active layer 105, Mg-doped Al _0.1 Ga _0.9 N layer 106, Mg
The point that the Mg-doped GaN layer 502 is grown only on the side surfaces of the ridge stripe structure composed of the doped GaN layer 501 to embed the ridge stripe structure almost flat.
It is different from the structure of the semiconductor laser device shown in FIGS.

In the example of FIG. 5, only one Mg-doped GaN layer is formed on the side of the ridge stripe structure, but Mg-doped Al _z Ga ₁ -zN is formed on the side of the ridge stripe structure. Two layers of (0 ≦ z <1) layer and Mg-doped GaN layer can also be formed. That is, the example of FIG. 5, Mg-doped _{Al z Ga 1-z N (} 0 ≦ z <1) layer, in the structure of two layers of Mg-doped GaN layer, Mg-doped Al _z
It can be considered that _{z of the} Ga _{1 -zN} (0 ≦ z <1) layer is “0”.

FIG. 6 is a diagram showing an example of a manufacturing process of the semiconductor laser device of FIG. Referring to FIG. 6, first, FIG.
(a) As shown in FIG.
0 ° AlN low temperature buffer layer 102, 2 μm thick Si
Doped n-type GaN layer 103, 0.5 μm-thick Si-doped n-type Al _0.1 Ga _0.9 N layer 104, non-doped InGa
An N-MQW active layer 105, a Mg-doped Al _0.1 Ga _0.9 N layer 106 having a layer thickness of 0.4 μm, and a Mg-doped GaN layer 501 having a layer thickness of 0.1 μm are sequentially formed by metal organic chemical vapor deposition.

Next, as shown in FIG.
On the aN layer 501, a striped SiN layer 6 having a width of 3 μm
Of the n-type GaN contact layer 10 from the surface of the Mg-doped GaN layer 501 using the SiN layer 601 as a mask.
Then, dry etching is performed until the number reaches 3, and a ridge stripe structure 202 is formed.

Next, using the above-mentioned striped SiN layer 601 as a mask, M
The g-doped GaN layer 502 is selectively grown to substantially flatten the substrate surface (FIG. 6C).

Subsequently, after removing the SiN layer 601,
By irradiating the entire substrate with, for example, an electron beam EB,
A low-resistance p-type region 109 is formed to a depth of about 0.5 μm from the surface (FIG. 6D). In the ridge stripe structure, the Mg-doped GaN layer 501 and the Mg-doped Al
_The resistance of all the _0.1 Ga _0.9 N cladding layers 106 is reduced. On the other hand, on the outside (side surface) of the ridge stripe structure, a region having a resistance of about 0.5 μm from the surface of the Mg-doped GaN layer 502 has a low resistance, but a lower region has high resistance.

Next, except for the region where the n-side electrode is formed,
A p-side electrode 110 made of Ni / Au and a Cr mask 204 are formed on the surface of the Mg-doped GaN layer 502 by vapor deposition.
(FIG. 6 (e)). Then, using the Cr mask 204 as a mask, dry etching is performed from the surface of the Mg-doped GaN layer 501 to reach the n-type GaN contact layer 103, and a Ti / A is formed on the exposed n-type GaN contact layer 103.
An n-side electrode 111 of l is formed (FIG. 6F).

In the semiconductor laser device manufactured by the above steps, the Mg-doped G
The aN layer 502 is grown to fill the ridge stripe structure almost flat, and the Mg-doped GaN layer 501 and the Mg-doped Al _x Ga above the In _y Ga _1-y N active layer 105.
_{The 1-x} N layer 106 and the Mg-doped Al _z Ga _{1 -z} N layer 502 have low resistance. On the other hand, outside the ridge stripe structure
Mg-doped Al _z Ga _1-z N layer 501 located below the InGaN active layer plane in (side) has become a left high resistance, the current (carrier) is concentrated in the ridge stripe structure of the low resistance region 109 Is injected into the InGaN active layer 105. The carriers injected into the InGaN active layer 105 are confined to the ridge stripe width by the hetero barrier, thereby suppressing the carriers from being diffused in the horizontal direction. Thereby, the threshold current of the element can be reduced.

Further, since the entire Mg-doped GaN layer on the surface of the laminated structure becomes a low-resistance p-type region by, for example, irradiation with an electron beam, the structure is smaller than that of the semiconductor laser device shown in FIGS. The contact area between the p-side electrode 110 and the p-type GaN layer can be increased. Therefore, the p-side contact resistance can be reduced, and the operating voltage of the element can be further reduced.

FIG. 7 is a diagram showing a fourth configuration example of the semiconductor laser device according to the present invention. In the semiconductor laser device of FIG. 7, at least n-type Al _x Ga ₁ -xN
(0 <x ≦ 1) cladding layer 104, In _y Ga _1-y N (0 ≦
y ≦ 1) A trapezoidal or triangular ridge stripe structure including the active layer 105 and the Mg-doped Al _x Ga ₁ -xN cladding layer 106 is formed by selective growth, and the side surface of the ridge stripe structure is Mg-doped GaN. Layer 50
2 and is almost flat, and I
Mg-doped Al above the n _y Ga _1-y N active layer 105
_The xGa ₁ -xN layer 106 and the Mg-doped GaN layer 502 are low-resistance p-type regions.

In the semiconductor laser device of FIG. 7, n-type Al _x
Ga _1-x N (0 <x ≦ 1) cladding layer 104, In _y Ga
_1-y N active layer (0 ≦ y ≦ 1) 105, Mg-doped Al _x Ga
A ridge stripe structure including the _1-xN cladding layer 106 is formed by selective growth. Therefore, FIGS.
As in the semiconductor laser device having the structure shown in _{FIG.
Since the} damage to the side surface of the _1-y N (0 ≦ y ≦ 1) active layer 105 can be made sufficiently small, In _y Ga _1-y N (0 ≦ y ≦
1) The crystal defects on the side surface of the active layer 105 are reduced, and the leakage current during operation can be reduced.

In the semiconductor laser device shown in FIG. 7, the ridge stripe structure is formed into a triangular shape or a trapezoidal shape having a narrow top by reducing the mask width during selective growth. The slope of the ridge stripe structure is
Since the growth rate is much slower than that on the (0001) plane, when the growth is performed by the metal organic chemical vapor deposition method after removing the selective growth mask, the ridge stripe structure is almost buried. And, on the entire surface of the flattened laminated structure,
For example, by irradiating an electron beam, In _y Ga _1-y
Mg-doped Al _x Ga _{1 -x} N above the N active layer 105
The resistance of the layer 106 and the Mg-doped GaN layer 502 is reduced. On the other hand, In _{y on} the outside (side surface) of the ridge stripe structure
The Mg-doped GaN layer 502 below the surface of the Ga _1-y N (0 ≦ y ≦ 1) active layer 105 remains high resistance. Therefore, the current (carrier) passes through the ridge stripe in the low-resistance region and passes through the In _y Ga _{1 -y} N (0 ≦ y ≦ 1) active layer 1.
05.

The semiconductor laser device of FIG. 7 has a point that the ridge stripe structure is formed by selective growth using the metal organic chemical vapor deposition method, and the cross-sectional shape of the ridge stripe structure is substantially triangular. Although the structure is different from the structure of the semiconductor laser device shown in FIGS. 5 and 6, since the entire surface of the laminated structure is a low-resistance p-type region, similar to the semiconductor laser device of FIGS. The p-side contact resistance can be reduced, and the operating voltage of the element can be further reduced.

On the other hand, the semiconductor laser device of FIG.
In addition to the effect shown in FIG. 6, since the ridge stripe structure is formed by selective growth, damage to the side surface of the InGaN active layer is small, crystal defects on the side surface of the InGaN active layer are reduced, and leakage current during operation is reduced. Can be reduced.

In the example of FIG. 7, only one Mg-doped GaN layer is formed on the side surface of the ridge stripe structure, but Mg-doped Al _z Ga ₁ -zN is formed on the side surface of the ridge stripe structure. Two layers of (0 ≦ z <1) layer and Mg-doped GaN layer can also be formed. That is, the example of FIG. 7, the Mg-doped _{Al z Ga 1-z N (} 0 ≦ z <1) layer, in the structure of two layers of Mg-doped GaN layer, Mg-doped Al _z
It can be considered that _{z of the} Ga _{1 -zN} (0 ≦ z <1) layer is “0”.

FIG. 8 is a diagram showing an example of a manufacturing process of the semiconductor laser device of FIG. Referring to FIG. 8, first, FIG.
As shown in FIG. 3A, an AlN low-temperature buffer layer 102 having a thickness of 200.degree. and a Si-doped n-type GaN contact layer 103 having a thickness of 2 .mu.m are sequentially formed on a sapphire substrate (0001) surface 101 by metal organic chemical vapor deposition. I do. Next, n-type Ga
An SiO ₂ film 401 is formed on the N contact layer 103. Then, using a photoresist as a mask, the SiO ₂ film 401 is removed by etching in a stripe shape in the <11-20> direction, and n-type GaN is formed into a stripe shape having a width of 1 μm.
The contact layer 103 is exposed (FIG. 8B).

Next, a 0.5 μm-thick Si-doped n-type A layer is formed on the n-type GaN contact layer 103 exposed in a stripe shape by selective growth by metal organic chemical vapor deposition.
l _0.1 Ga _0.9 N layer 104, non-doped InGaN-MQ
W active layer 105, Mg-doped Al _{0.1 having} a thickness of 0.5 μm
The Ga _0.9 N layers 106 are sequentially stacked (FIG. 8C). By using the selective growth, crystal growth is not basically performed on the SiO ₂ film 401, and the ridge stripe structure 202 having a substantially triangular cross section is formed.

Next, after removing the SiO ₂ film 401,
The Mg-doped GaN layer 502 is grown by metal organic chemical vapor deposition. The slope of the ridge stripe structure is (000
1) Since the growth rate is much slower than on the surface, the n-type GaN contact layer 1 exposed by removing the SiO ₂ film 401
The growth of the Mg-doped GaN layer 502 mainly proceeds on the (0001) plane of No. 03. As a result, the ridge stripe structure is almost flatly buried (FIG. 8D).

Subsequently, by irradiating the entire substrate with, for example, an electron beam EB, the Mg-doped layer is changed to a low-resistance p-type region 109 to a depth of about 0.5 μm from the surface (FIG. 8E). . In the ridge stripe structure, Mg
The resistance of all the doped Al _0.1 Ga _0.9 N cladding layers 106 is reduced. On the other hand, outside the ridge stripe structure, a region of about 0.5 μm from the surface of the Mg-doped GaN layer 502 has a low resistance, but a region below it has a high resistance.

Finally, a p-side electrode 110 made of Ni / Au is formed on the surface of the Mg-doped GaN layer 502.
Dry etching is performed from the surface of the g-doped GaN layer 502 to the n-type GaN contact layer 103 to form an n-side electrode 111 made of Ti / Al on the exposed n-type GaN contact layer 103 (FIG. 8F). ).

In the semiconductor laser device manufactured in the above steps, the Mg-doped GaN layer 502 located below the surface of the InGaN-MQW active layer 105 on the outer side (side surface) of the triangular ridge stripe structure has a high resistance. Current is concentrated on the ridge stripe structure and
Carriers are injected into the GaN-MQW active layer 105.

Further, since the Mg-doped GaN layer 502 on the surface of the laminated structure becomes a low-resistance p-type region by, for example, electron beam irradiation, a large contact area between the p-side electrode 110 and the p-type GaN layer is required. Can be. Therefore, the p-side contact resistance can be reduced, and the operating voltage of the element can be further reduced.

Further, since the ridge stripe structure is formed by selective growth, damage to the side surface of the InGaN-MQW active layer 105 can be reduced as in the device shown in FIG. It is possible to reduce the leak current.

As described above, in the semiconductor laser devices of FIGS. 7 and 8, in addition to the effects described above with reference to FIGS. 5 and 6, the ridge stripe structure is formed by selective growth.
The damage to the side surface of the nGaN active layer is small, and InG
The crystal defects on the side surfaces of the aN active layer are reduced, and the leakage current during operation can be reduced.

FIG. 9 is a diagram showing a fifth configuration example of the semiconductor laser device of the present invention. In the semiconductor laser device shown in FIG. 9, at least n-type Al _x Ga ₁ -xN (0 <
x ≦ 1) cladding layer 104, In _y Ga _1-y N (0 ≦ y ≦
1) A trapezoidal or triangular ridge stripe structure including the active layer 105 is formed by selective growth.
The _ny Ga _1-y N (0 ≦ y ≦ 1) active layer 105 is provided near the top of the ridge stripe structure, and the ridge stripe structure is formed of an Mg-doped Al _x Ga _1-x N layer 901 and M
in g-doped GaN layer 902 is embedded in the substantially flat, Mg-doped Al _x Ga _1-x N layer 901 of a laminated structure surface to the vicinity of the In _y Ga _1-y N active layer 105, Mg-doped Al _x Ga _{1- xN} layer 106 (as described below, in this example,
The Mg-doped Al _x Ga _1-x N layer 901 is made of Mg-doped Al _x
Ga _1-x N layer 106) has a low resistance p-type region.

That is, in the semiconductor laser device of FIG.
The stripe width for selective growth is made extremely narrow, for example, 1 μm or less, to form a triangular or narrow trapezoidal ridge stripe structure with a narrow top, and an InGaN active layer 105 is formed near the top of the ridge stripe structure. It differs from the structure of the semiconductor laser device of FIG. 7 in that it is buried in an Al _x Ga ₁ -xN (0 <x ≦ 1) layer 901. According to the above-mentioned structure, the width of the InGaN active layer 105 can be extremely narrowed to several thousand degrees or less, so that carriers can be concentrated, and the threshold current of the device can be further reduced.

More specifically, in the semiconductor laser device of FIG. 9, the ridge stripe structure has a stripe width of 0.5 μm.
Formed on the SiO ₂ stripe window of In _y Ga
_1-y N (0 ≦ y ≦ 1) active layer (InGaN-MQW active layer)
The width of 105 is very narrow, about 0.2 μm. In _y Ga _1-y N (0 ≦ y ≦ 1) active layer (InGaN-
The periphery of the MQW active layer 105 is Mg-doped Al _x Ga
_1-x N layer (for example, Mg-doped Al _0.1 Ga _0.9 N layer) 901
And the carrier is InG by the hetero barrier.
It is confined in the aN-MQW active layer 105. Therefore,
Since the carrier can be concentrated in a small area,
The threshold current of the device can be reduced.

Here, the Mg-doped Al _x Ga ₁ -xN layer (for example, Mg-doped Al _0.1 Ga _0.9 N layer) 901 is made of InG
The crystal is grown to a thickness of 0.4 μm above the aN-MQW active layer 105 and also serves as the upper cladding layer 106.

On the Mg-doped Al _x Ga ₁ -xN layer (for example, Mg-doped Al _0.1 Ga _0.9 N layer) 901,
A doped GaN contact layer 902 is laminated with a layer thickness of 0.1 μm. In FIG. 9, a shaded region 109 is a p-type region that has been reduced in resistance to a depth of about 0.5 μm from the element surface by irradiating, for example, an electron beam. Outside the triangular ridge stripe structure (side surface), In _y Ga _1-y N
(0 ≦ y ≦ 1) Active layer (InGaN-MQW active layer) 105
Mg-doped Al _x Ga _1-x N layer (for example, Mg
Since the doped Al _0.1 Ga _0.9 N layer 901 remains at a high resistance, the current is concentrated on the ridge stripe structure.

Since the Mg-doped GaN contact layer 902 on the surface of the laminated structure is a low-resistance p-type region,
The contact area with the p-side electrode 110 can be increased. Therefore, the p-side contact resistance can be reduced, and the operating voltage of the element can be further reduced.

As described above, the semiconductor laser device of FIG.
In addition to the effects described above with reference to FIGS. 7 and 8, In _y Ga _1-y N
(0 ≦ y ≦ 1) The active layer 105 is made of Mg-doped Al _x Ga _1-x N
Since it is formed near the top of the trapezoidal or triangular ridge stripe structure surrounded by the layer 901, In _y G
The width of the a _1-y N (0 ≦ y ≦ 1) active layer 105 can be made very narrow to concentrate the carriers, and the threshold current of the device can be further reduced.

[0082]

As described above, according to the first aspect of the present invention, at least n-type Al _x Ga
_1-x N (0 <x ≦ 1) cladding layer, In _y Ga _1-y N (0 ≦ y
≦ 1) A ridge stripe structure including an active layer and a p-type Al _x Ga ₁ -xN cladding layer is formed, and a Mg-doped Al _x Ga _{1 -x} N layer and a Mg-doped GaN layer are sequentially stacked on the entire surface of the substrate. are, Mg-doped Al _x Ga _1-x N layer on the ridge stripe structure, Mg-doped GaN layer has a low resistance p-type region, Mg-doped Al _x outside of the ridge stripe structure 202 (side surface) Since the Ga _1-x N layer and the Mg-doped GaN layer remain at high resistance, current is concentrated on the ridge stripe structure having low resistance, and carriers are injected into the active layer. The hetero-barrier narrows the width of the ridge stripe, and suppresses the diffusion of carriers in the horizontal direction. This allows
The threshold current of the device can be reduced.

According to the second aspect of the present invention, at least an n-type Al _x Ga ₁ -xN (0 <x ≦ 1) cladding layer and an In _y Ga _{1 -y} N (0 ≦ y ≦ 1) Active layer, p-type A
A ridge stripe structure including a l _x Ga _1-x N cladding layer is formed by selective growth, and a M
A g-doped Al _x Ga _1-x N layer and a Mg-doped GaN layer are sequentially stacked, and the Mg-doped Al _x Ga _1-x N layer and the Mg-doped GaN layer on the ridge stripe structure are formed as a low-resistance p-type region. Since the ridge stripe structure is formed by selective growth, In _y Ga _1-y N (0 ≦ y ≦
1) The side surface of the active layer is not damaged by dry etching or heat treatment, and In _y Ga _1-y N (0 ≦ y
.Ltoreq.1) Crystal defects on the side surface of the active layer are reduced, and it is possible to reduce leakage current during device operation.

According to the third aspect of the present invention, at least an n-type Al _x Ga ₁ -xN (0 <x ≦ 1) cladding layer and an In _y Ga _{1 -y} N (0 ≦ y ≦ 1) A ridge stripe structure including an active layer, a Mg-doped Al _x Ga ₁ -xN cladding layer, and a Mg-doped GaN contact layer is formed.
1 _z Ga _{1 -zN} (0 ≦ z <1) layer, almost flat buried with Mg-doped GaN layer, and In _y G
Mg-doped GaN layer above a _1-y N active layer, Mg
The doped Al _x Ga _{1 -x} N layer and the Mg doped Al _z Ga _{1 -z} N layer are p-type regions having low resistance, and are formed on the outer side (side surface) of the ridge stripe structure and below the active layer surface. since doped Al _z Ga _1-z N layer is stuck in the high resistance, the current (carriers) are injected into the InGaN active layer 105 concentrates on the ridge stripe structure of the low-resistance region, which is injected into the active layer Carriers are narrowed to the width of the ridge stripe by the hetero-barrier, thereby suppressing carriers from being diffused in the horizontal direction. Thereby, the threshold current of the element can be reduced. Further, the entire Mg-doped GaN layer on the surface of the laminated structure is a low-resistance p-type region.
The contact area between the p-side electrode and the p-type GaN layer can be increased as compared with the structure of the semiconductor laser device of the second aspect. Therefore, the p-side contact resistance can be reduced, and the operating voltage of the element can be further reduced.

According to the fourth aspect of the present invention, at least an n-type Al _x Ga ₁ -xN (0 <x ≦ 1) cladding layer and an In _y Ga _{1 -y} N (0 ≦ y ≦ 1) A trapezoidal or triangular ridge stripe structure including an active layer and an Mg-doped Al _x Ga ₁ -xN cladding layer is formed by selective growth, and the side surface of the ridge stripe structure is Mg-doped Al _z Ga. _1-z N (0 ≦ z <1) layer, Mg-doped GaN
Embedded almost flat with a layer, and I
a Mg-doped GaN layer above the n _y Ga _1-y N active layer,
Mg-doped Al _x Ga _1-x N layer, Mg-doped Al _z Ga _1-z
Since the N layer is a low-resistance p-type region and the entire surface of the laminated structure is a low-resistance p-type region, the p-side contact resistance is reduced as in the semiconductor laser device of claim 3. As a result, the operating voltage of the element can be further reduced.
Further, in this semiconductor laser device, in addition to the above-described effect of claim 3, since the ridge stripe structure is formed by selective growth, damage to the side of the active layer is small, and crystal defects on the side of the active layer are reduced. As a result, the leakage current during operation can be reduced.

According to the fifth aspect of the present invention, In
_y Ga _1-y N (0 ≦ y ≦ 1) active layer is Mg-doped Al _x Ga
_Since it is formed near the top of the trapezoidal or triangular ridge stripe structure surrounded by the _1-xN layers, In _y G
The width of the a _1-y N (0 ≦ y ≦ 1) active layer can be made very narrow to concentrate the carriers, and the threshold current of the device can be further reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first configuration example of a semiconductor laser device according to the present invention.

FIG. 2 is a diagram illustrating an example of a manufacturing process of the semiconductor laser device of FIG. 1;

FIG. 3 is a diagram showing a second configuration example of the semiconductor laser device according to the present invention.

FIG. 4 is a diagram illustrating an example of a manufacturing process of the semiconductor laser device of FIG. 3;

FIG. 5 is a diagram showing a third configuration example of the semiconductor laser device according to the present invention.

6 is a diagram illustrating an example of a manufacturing process of the semiconductor laser device of FIG. 5;

FIG. 7 is a diagram showing a fourth configuration example of the semiconductor laser device according to the present invention.

8 is a diagram illustrating an example of a manufacturing process of the semiconductor laser device of FIG. 7;

FIG. 9 is a diagram showing a fifth configuration example of the semiconductor laser device according to the present invention.

FIG. 10 is a diagram showing a conventional gallium nitride based semiconductor laser device.

FIG. 11 is a sectional view of another conventional gallium nitride based semiconductor laser device.

FIG. 12 is a cross-sectional view of another conventional gallium nitride based semiconductor laser device.

[Explanation of symbols]

101 substrate 102 AlN buffer layer 103 Si doped n-type GaN contact layer 104 n-type _{Al x Ga 1-x N (} 0 <x ≦ 1) cladding layer _{105 In y Ga 1-y N} (0 ≦ y ≦ 1) active layer 106 p-type Al _x Ga _1-x n cladding layer 107 Mg-doped Al _x Ga _1-x n layer 108 Mg-doped GaN layer 109 low-resistance p-type region 110 p-side electrode 111 n-side electrode 201 dry etching mask 202 ridge stripe structure 203 Photoresist 204 Cr mask 401 SiO ₂ layer 501 Mg-doped GaN contact layer 502 Mg-doped GaN buried layer 601 SiN layer 901 Mg-doped Al _x Ga _1-x N layer 902 Mg-doped GaN contact layer

Claims (5)

[Claims] At least an n-type Al _x Ga film is formed on a substrate.
_1-x N (0 <x ≦ 1) cladding layer, In _y Ga _1-y N (0 ≦ y
≦ 1) A ridge stripe structure including an active layer and a p-type Al _x Ga ₁ -xN cladding layer is formed, and a Mg-doped Al _x Ga _{1 -x} N layer and a Mg-doped GaN layer are sequentially stacked on the entire surface of the substrate. Wherein the Mg-doped Al _x Ga ₁ -xN layer and the Mg-doped GaN layer on the ridge stripe structure are low-resistance p-type regions. 2. At least n-type Al _x Ga is formed on a substrate.
_1-x N (0 <x ≦ 1) cladding layer, In _y Ga _1-y N (0 ≦ y
≦ 1) A ridge stripe structure including an active layer and a p-type Al _x Ga ₁ -xN cladding layer is formed by selective growth, and a Mg-doped Al _x Ga _{1 -x} N layer, M
A semiconductor laser device in which g-doped GaN layers are sequentially stacked, and the Mg-doped Al _x Ga ₁ -xN layer and the Mg-doped GaN layer on the ridge stripe structure are low-resistance p-type regions. . 3. At least n-type Al _x Ga is formed on a substrate.
_1-x N (0 <x ≦ 1) cladding layer, In _y Ga _1-y N (0 ≦ y
≦ 1) Active layer, Mg-doped Al _x Ga ₁ -xN cladding layer,
A ridge stripe structure including an Mg-doped GaN contact layer is formed, and the side surface of the ridge stripe structure is formed of a Mg-doped Al _z Ga _{1 -zN} (0 ≦ z <1) layer,
It is almost flatly buried with a doped GaN layer, and Mg-doped GaN layer, Mg-doped Al _x Ga _1-x N layer, Mg-doped Al _z Ga above the In _y Ga _1-y N active layer from the surface of the laminated structure. A semiconductor laser device, wherein the _1-z N layer is a low-resistance p-type region. 4. At least n-type Al _x Ga on a substrate
_1-x N (0 <x ≦ 1) cladding layer, In _y Ga _1-y N (0 ≦ y
≦ 1) A trapezoidal or triangular ridge stripe structure including an active layer and a Mg-doped Al _x Ga ₁ -xN cladding layer is formed by selective growth, and the side surface of the ridge stripe structure is Mg-doped Al _z Ga _{1. -z} N (0 ≦ z <1)
, A Mg-doped GaN layer above the In _y Ga _1-y N active layer from the surface of the laminated structure, a Mg-doped Al _x Ga _1-x N layer,
A semiconductor laser device characterized in that the Mg-doped Al _z Ga _{1 -zN} layer is a low-resistance p-type region. 5. At least n-type Al _x Ga on a substrate
_1-x N (0 <x ≦ 1) cladding layer, In _y Ga _1-y N (0 ≦ y
≦ 1) trapezoidal or triangular ridge stripe structure including an active layer is formed by selective growth, an In _y
The Ga _1-y N (0 ≦ y ≦ 1) active layer is provided near the top of the trapezoidal or triangular ridge stripe structure,
Furthermore, the ridge stripe structure is Mg-doped Al _x Ga _1-x
The N layer and the Mg-doped GaN layer are buried almost flat, and the M layer extends from the surface of the laminated structure to the vicinity of the In _y Ga _1-y N active layer.
A semiconductor laser device wherein a g-doped GaN layer and a Mg-doped Al _x Ga ₁ -xN layer are low resistance p-type regions.