JPH08236870A - Semiconductor laser device and its manufacture - Google Patents

Abstract

PURPOSE: To make it possible to produce a semiconductor laser device having good electrical characteristics and high reliability with a good yield by making a plane on a region directly below a laser oscillating region on a substrate and by constituting other regions only from slopes having specific orientations as surfaces. CONSTITUTION: This semiconductor laser device is laminated with an n-type GaAs substrate 1, an n-type ZnSe buffer layer 2, an n-type ZnSSe clad layer 3, an active layer 4 made of CdZnSe, a p-type ZnSSe clad layer 5, a heavily deped p-type ZnSe layer 6 as a contact layer in this order. Here, a region 1a directly below a laser oscillating region on the surface of the substrate 1 is made of a recessed portion, its bottom surface has a flat surface shape, and other regions in which the grating region 1b comprises slopes with the (111) plane of the substrate as surfaces; that is, it is constituted with a slope 1c only having an angle of +54.7 deg. and -54.7 deg. with the region 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device having an active layer sandwiched between cladding layers of different conductivity types on a semiconductor substrate and emitting a laser beam from a laser oscillation region of the active layer, and a manufacturing method thereof. More particularly, the present invention relates to a semiconductor laser device suitable for a type for obtaining a blue laser by using a II-VI group compound semiconductor and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a blue laser was prepared by growing a zinc selenide (ZnSe) crystal on a gallium arsenide (GaAs) substrate as a II-VI group compound semiconductor epitaxial crystal and further introducing nitrogen (N) as a dopant. In recent years, attention has been paid to a method and an apparatus for forming a p-type crystal for obtaining the same, and an example thereof is disclosed in JP-A-62-88329. Further, according to DePuydt et al. Of the United States, a method has been proposed in which an active nitrogen beam is generated by an rf plasma excitation cell by the MBE method to realize nitrogen doping of 1 × 10 ¹⁸ cm ⁻³ (Appl. Phy.
s. Lett. 57, 2127 (1991)), which suggests that a p-type crystal with low resistance can be obtained.

In such a semiconductor laser device, it is necessary to provide a so-called current constriction structure inside the laser device in order to perform efficient oscillation. For example, JP-A-5-19996, JP-A-6-97590, or JP-A-6-975.
Japanese Patent Laid-Open No. 72-72 discloses a structure in which a high resistance layer called a current confinement layer or a block layer is formed on or under any one of the cladding layers inside the laser device to concentrate the current in a predetermined region of the active layer. Has been done.

However, the high resistance layer is, for example, n
P-type doped semiconductor for the cladding layer, p
The n-type cladding layer is formed as an n-type doped semiconductor, and not only is its film formation, doping and patterning troublesome, but the doping is also performed during the film formation (crystal growth) process of each layer. Further, since the patterning process is interposed, the surface of the layer on which the epitaxial crystal is grown is easily contaminated when the substrate is moved, and there is a problem that the film quality is deteriorated. Particularly, the II-VI group epitaxial crystal growth layer is easily contaminated, and the above problem becomes more serious in the II-VI group compound semiconductor laser device. Also,
The epitaxial crystal growth layer is damaged by heat treatment during doping, etc., which also deteriorates the film quality.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and its main object is to provide a semiconductor laser device having good electrical characteristics and high reliability, and a semiconductor laser device having the same. It is an object of the present invention to provide a method of manufacturing a semiconductor laser device capable of manufacturing a semiconductor laser device with a high yield.

[0006]

According to the present invention, the above-mentioned object is achieved by providing a first conductivity type first clad layer, an active layer, and a second conductivity type second clad on a first conductivity type semiconductor substrate. A semiconductor laser device having a layer and a contact layer in this order, and applying a voltage between the substrate and the contact layer to emit laser light from the laser oscillation region of the active layer, Of the semiconductor laser device and the semiconductor substrate of the first conductivity type, wherein the region immediately below the laser oscillation region of is a plane and the other region is composed only of an inclined surface having the (111) plane as a surface. A first conductive type first clad layer, an active layer, a second conductive type second clad layer, and a contact layer in this order, and a voltage is applied between the substrate and the contact layer. From the laser oscillation region of the active layer A method for manufacturing a semiconductor laser device that emits laser light, comprising exposing or masking the entire region of the surface of the substrate immediately below the laser oscillation region, and masking the other region at predetermined intervals and widths. By anisotropically etching the surface of the substrate, the entire region immediately below the laser oscillation region is made flat and the other region is made up of only slopes having the (111) plane as its surface. This is achieved by providing a method for manufacturing a semiconductor laser device, which is characterized in that the above layers are sequentially laminated on the surface.

[0007]

As described above, the region directly below the laser oscillation region is made flat by anisotropic etching of the substrate surface, and the other region is constituted only by the slope having the (111) plane of the substrate as the surface. , MBE method, MOMBE method, CB
By forming a clad layer, an active layer, etc. by the E method or the like to form a laser oscillation structure, for example, the p-type clad layer becomes a high resistance layer on the (111) plane of the substrate, so that the substrate before crystal growth A current constriction structure can be obtained only by the etching process for.

[0008]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic sectional structure of a semiconductor laser device made of a II-VI group compound semiconductor according to a first embodiment of the present invention. This semiconductor laser device includes an n-type gallium arsenide (GaAs) substrate 1 and an n-type Zn
Se buffer layer 2, n-type ZnSSe first cladding layer 3, CdZnSe active layer 4, p-type Zn
The second cladding layer 5 of SSe and the heavily doped p-type ZnSe layer 6 as a contact layer are laminated in this order. An Au electrode 7 is formed on the upper layer of the heavily doped p-type ZnSe layer 6 by vapor deposition. In addition, n-type G
An Au / Ge (germanium) electrode layer 8 is formed on the back surface of the aAs substrate 1.

Here, the region 1a directly below the laser oscillation region on the surface of the substrate 1 is made of a concave portion and its bottom surface is flat, and the other region, that is, the grating region 1b is the (111) plane of the substrate. The surface is a slope 1c, that is, only the slope 1c forming an angle of + 54.7 ° and −54.7 ° with respect to the region 1a. Further, each of the upper layers is also formed in a shape corresponding to the surface shape of the substrate 1. Therefore, in the crystal structure of the substrate 1, in the grating region 1b formed only of the (111) plane, the upper layer thereof becomes a high resistance layer, and a current hardly occurs, and the current confinement structure is concentrated in the region 1a.

The manufacturing procedure of the semiconductor laser device of this embodiment will be described below. First, on the n-type GaAs substrate 1,
Area 1 by photolithography and wet etching
A is recessed and a grating region 1b is formed. Here, as shown in FIG. 2, the region 1a is exposed,
By forming the resist 9 on the grating region 1b at a predetermined interval and width and anisotropically etching the region 1a, the region 1a is formed of a concave portion and the bottom surface thereof is flat.
In the region 1b, the substrate 1 is formed in which only the slope having the (111) plane as the surface remains. Then, on the substrate 1, an n-type ZnSe buffer layer 2 and an n-type ZnSSe first cladding layer 3 are formed.
An active layer 4 made of CdZnSe, and p-type ZnSSe
The second clad layer 5 and the heavily doped p-type ZnSe layer 6 are sequentially formed by the MBE method. Here, the thickness of the buffer layer 2 is 1000Å, and the thickness of the first cladding layer 3 is 2.0 μm (composition: ZnS0.07Se0.9).
3), the thickness of the active layer 4 is 100Å (composition: Cd0.1Z
n0.9Se), and the thickness of the second cladding layer 5 is 1.5 μm.
m (composition: ZnS0.07Se0.93), the highly-doped p-type ZnSe layer 6 has a thickness of 1000Å, and a carrier concentration is 1 × 10 ¹⁸ cm ^−3, and crystals are sequentially grown.
In addition, chlorine (Cl) is used as a dopant for each of the above n-type layers,
Nitrogen (N) was used as a dopant for each p-type layer.

Finally, an Au electrode 7 is formed on the heavily doped p-type ZnSe layer 6 and an Au / Ge (germanium) electrode layer 8 is formed on the back surface of the substrate 1.

FIG. 3 shows a schematic sectional structure of a semiconductor laser device according to a second embodiment of the present invention. In the structure of this embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, the region 11a directly below the laser oscillation region on the surface of the substrate 11 is formed of a convex portion and the bottom surface thereof is flat. Then, the grating region 11b becomes (1
11) Slope with the surface as the surface, that is, with respect to the region 11a
It is composed of only the slope 11c forming an angle of 54.7 ° and -54.7 °. Other structures are the same as those of the first embodiment.

The manufacturing procedure of the semiconductor laser device of this embodiment will be described below. First, the n-type GaAs substrate 11
Then, the region 11a is formed to be convex and the grating region 11b is formed by photolithography and wet etching. Here, as shown in FIG. 4, the entire area of the region 11a is covered with the resist 19, and the grating region 11 is formed.
By forming resists 19 on b at a predetermined interval and width and performing anisotropic etching, the region 11a is formed of a convex portion and the bottom surface thereof has a planar shape, and the region 11b is (1
11) A substrate 11 is formed in which only the sloped surface is the surface. The procedure for forming the other layers is the same as in the first embodiment.

In each of the above embodiments, M is used for crystal growth of each layer.
Although the BE method is used, similar results can be obtained by the MONBE method or the CBE method, for example. The same result can be obtained even if the substrate is p-type and each layer is pn-inverted. In addition, although the active layer is in direct contact with each clad layer in each of the above-mentioned embodiments, an optical waveguide layer of about 0.4 μm may be interposed between each clad layer and the active layer. At this time, the conductivity type of each optical waveguide layer is the same as the conductivity type of the cladding layer in contact with it. Similarly, it goes without saying that the same result can be obtained by interposing an arbitrary layer for changing the electrical or optical characteristics between the layers as required.

[0016]

As is apparent from the above description, according to the semiconductor device and the method of manufacturing the same according to the present invention, the region immediately below the laser oscillation region has a planar shape by anisotropic etching of the substrate surface, and Areas other than (1
11) Only the slope with the surface as the surface,
Since a laser oscillation structure is formed by forming a clad layer, an active layer, etc. by the MBE method, the MOMBE method, the CBE method, etc., for example, the p-type clad layer becomes a high resistance layer on the (111) plane of the substrate. , The current confinement structure can be obtained only by etching the substrate before crystal growth, and the number of manufacturing steps can be reduced and the adverse effects on each layer due to doping, etching, etc. can be minimized. A highly efficient semiconductor laser device can be manufactured with high yield.

[Brief description of drawings]

FIG. 1 is a II-V in a first embodiment according to the present invention.
Sectional drawing of the principal part of the semiconductor laser device which consists of a group I compound semiconductor.

FIG. 2 is a diagram illustrating a manufacturing procedure of the semiconductor laser device of FIG.

FIG. 3 II-V in a second embodiment according to the present invention
Sectional drawing of the principal part of the semiconductor laser device which consists of a group I compound semiconductor.

FIG. 4 is a diagram illustrating a manufacturing procedure of the semiconductor laser device of FIG.

[Explanation of symbols]

 1 n-type GaAs substrate 1a region immediately below laser oscillation region 1b grating region 1c slope 2 buffer layer made of n-type ZnSe 3 first clad layer made of n-type ZnSSe 4 active layer made of CdZnSe 5 second made of p-type ZnSSe Clad layer 6 Highly doped p-type ZnSe layer (contact layer) 7 Au electrode layer 8 Au / Ge electrode layer 9 Resist 11 n-type GaAs substrate 11a Region immediately below laser oscillation region 11b Grating region 11c Slope

Continuation of the front page (72) Inventor Satoshi Fujii 5-10-1, Fuchinobe, Sagamihara-shi Nippon Steel Co., Ltd. Inside Electronics Research Laboratory

Claims (2)

[Claims] 1. A substrate having a first conductivity type first clad layer, an active layer, a second conductivity type second clad layer, and a contact layer in this order on a first conductivity type semiconductor substrate. A semiconductor laser device that emits laser light from a laser oscillation region of the active layer by applying a voltage between the contact layer and the contact layer, and the region directly below the laser oscillation region on the substrate is a flat surface The semiconductor laser device is characterized in that the region (1) is composed of only a slope having the (111) plane as its surface. 2. A substrate having a first conductivity type first cladding layer, an active layer, a second conductivity type second cladding layer, and a contact layer in this order on a first conductivity type semiconductor substrate. A method for manufacturing a semiconductor laser device in which a laser beam is emitted from a laser oscillation region of the active layer by applying a voltage between the contact layer and the contact layer, and the entire region of the substrate surface immediately below the laser oscillation region is exposed. Or masking and masking the other regions at a predetermined interval and width to anisotropically etch the substrate surface, thereby making the entire region immediately below the laser oscillation region a plane and A method for manufacturing a semiconductor laser device, wherein a region is constituted by only a slope having a (111) plane as a surface, and the respective layers are sequentially laminated on the surface.