JPH0677585A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a decrease in yield due to dusts adhering surface of a semiconductor substrate by reducing number of introducing and removing the substrate into and from a growing apparatus in a lateral mode control type visible light semiconductor laser using compound semiconductor such as AlGaInP series. CONSTITUTION:The semiconductor laser comprises an upper p-type clad layer 8 formed in a protrusion stripe state, a p-type current uniform layer 10 formed on the stripe of the layer 8a and having lower resistivity than that of the layer 8, a current narrowing layer 11 in which an oblique part 112 formed on the layers 8, 10 becomes p type and the other parts 111, 112 become n type, and a p-type contact layer 12 formed on the layer 11. The layer 11 in which the part 112 is the p type and the other parts 111, 113 are n type can be formed by simultaneously doping it with n-type impurity and p-type impurity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse mode control type visible light semiconductor laser device using a compound semiconductor such as AlGaInP.

[0002]

2. Description of the Related Art In recent years, a 0.6 μm band visible light semiconductor laser device has been greatly expected as a light source for realizing high performance of optical information processing devices such as POS, optical disk devices and laser printers. Such a visible light semiconductor laser device is required to have a low threshold current and high efficiency, and also to be manufactured at a high yield and at a low cost. Therefore, an AlGaInP-based laser device is promising. Has been done.

However, unlike the GaAs / AlGaAs-based semiconductor laser device which has been widely used in the past, the AlGaInP-based laser device does not allow a semiconductor layer containing Al to grow on the semiconductor layer containing Al with good crystallinity. It's extremely difficult. Therefore, buried hetero type (BH)
It is difficult to realize a refractive index change by embedding a semiconductor material containing Al as in a laser device. Therefore, the lateral mode control type AlG that has been practically used in the past
In the aInP-based laser device, the active layer is flat, and the upper cladding layer is formed into a mesa stripe type to change the refractive index in the lateral direction.

FIG. 4 shows a conventional lateral mode control type semiconductor laser.
It is a structure explanatory view of the device. In this figure, 21 is n
-GaAs substrate, 22 is n- (Al_0.7Ga_0.3) _0.5
In_0.5P-clad layer, 23 is undoped Ga_0.5In
_0.5P active layer, 24 is p- (Al_0.7Ga_0.3)_0.5I
n_0.5P first cladding layer, 25 is p- (Al _0.7Ga
_0.3)_0.5In_0.5P second clad layer, 26 is p-Ga
_0.5In_0.5P spike prevention layer, 27 is p-GaAs
Buffer layer, 28 is a p-GaAs current blocking layer, and 29 is
A p-GaAs contact layer is shown.

With reference to this structure explanatory view, a method of manufacturing a conventional lateral mode control type AlGaInP semiconductor laser device and its structure will be described by taking a ridge type loss guide laser device as an example.

To manufacture this conventional semiconductor laser device
First, on the Si-doped n-GaAs substrate 21, S
e-doped n- (Al_0.7Ga_0.3)_0.5In_0.5P class
Dead layer 22, undoped Ga_0.5In_0.5P active layer 2
3, Mg-doped p- (Al_0.7Ga_0.3)_0.5In_0.5
P first cladding layer 24, Mg-doped p- (Al_0.7Ga
_0.3)_0.5In_0.5Semiconductor that becomes the second clad layer 25
Layer, Zn-doped p-Ga _0.5In_0.5P spike prevention layer
26, semiconductor layer, Zn-doped p-GaAs buffer
A semiconductor layer to be the layer 27 is sequentially grown.

Next, the p-GaAs buffer layer 27 and p
-Ga _0.5 In _0.5 P spike prevention layer 26 and p- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P The second cladding layer 25 is selectively etched to form a mesa.

A Se-doped p-GaAs current blocking layer 28 is grown thereon, and the central portion thereof is removed by etching to expose the top of the p-GaAs buffer layer 27.

A Zn-doped p-GaAs contact layer 29 is grown on it. Then, p-type and n-type electrodes are formed to complete the process.

In this structure, the buried layers on both ends of the mesa stripe are p-GaAs current blocking layers 28 that absorb light, and have a loss guide structure.

[0011]

However, in the semiconductor laser device having the structure as shown in FIG. 4, p-GaA is used.
Since the s current blocking layer 28 is formed by embedded growth by the MOPVE method, it is necessary to grow the semiconductor layer three times.

As described above, when the semiconductor substrate is moved in and out of the MOPVE growth apparatus many times, it is inevitable that dust is attached to the surface of the semiconductor substrate in and out of the growth apparatus, which causes crystal defects. There is a problem in that the yield rate decreases due to an increase in the crystal growth defect rate. An object of the present invention is to reduce the number of times a semiconductor substrate is taken in and out of a growth apparatus, thereby preventing a decrease in yield due to dust attached when the semiconductor substrate is taken in and out of the growth apparatus.

[0013]

In a semiconductor laser device according to the present invention, an upper p-type clad layer formed in a convex stripe shape on an active layer and a convex stripe of the p-type clad layer are formed. In addition, the p-type current equalizing layer having a lower resistivity than the p-type cladding layer, and the slope portion formed on the p-type cladding layer and the current equalizing layer are p-type and the other portions are n-type. The current confinement layer and the p-type contact layer formed on the current confinement layer are used.

In this case, the hetero spike prevention layer is provided between the p-type current equalizing layer and the p-type cladding layer, and the hetero spike prevention layer is not provided between the slope of the p-type cladding layer and the current constriction layer. be able to.

Further, in this case, the material of the current confinement layer and the material of the current equalizing layer may be GaAs or GaInP, and the cladding layer may be AlGaInP or AlInP.

In this case, the substrate is the (100) plane, the slopes of the p-type cladding layer and the current equalizing layer are between the (411) A plane and the (111) A plane, and the current confinement layer is the p-type. A structure formed by supplying impurities and n-type impurities simultaneously can be adopted.

In this method of manufacturing a semiconductor laser device, a convex surface having a slope between the (411) A surface and the (111) A surface is formed on the active layer formed on the (100) surface of the semiconductor substrate. Step of forming a clad layer made of a stripe-shaped p-type semiconductor layer, and forming a current equalizing layer made of a p-type semiconductor layer having a resistivity lower than that of the clad layer on top of the clad layer made of the p-type semiconductor layer On the cladding layer and the current equalizing layer, the slope portion of the cladding layer is p-type, and the other portion is an n-type current confinement layer.
The step of forming by supplying the type impurities and the n-type impurities at the same time and the step of forming the p-type contact layer on the current confinement layer were adopted.

[0018]

As described above, in order to reduce the number of times the semiconductor substrate is taken in and out of the growth apparatus, the plane orientation dependence of the semiconductor crystal of the incorporation rate of p-type (dopant) impurities and n-type impurities is utilized. By simultaneously supplying (simultaneous doping) p-type and n-type impurities, a current confinement layer composed of the n-type current block layers 11 ₁ and 11 ₃ and the p-type current channel layer 11 ₂ is formed by one growth. The p-GaAs contact layer 12 may be subsequently grown thereon.

FIG. 1 is an explanatory diagram of AlGaInP-doped plane orientation dependence of Se and Zn. The horizontal axis of this figure is (Al
_It is the inclination (degree) from the (100) plane to the (111) A plane of the _0.7 Ga _0.3 ) _0.5 In _0.5 P substrate, and the vertical axis represents the carrier concentration (cm ^-3 ).

As shown in this explanatory diagram, (10
The carrier concentration of the carrier layer of the simultaneous doping layer on the (0) plane and the (411) A plane can be made close to the carrier concentration of the single doping, and the plane having the (100) plane and the slope having the (411) A plane are inclined. AlG consisting of faces
When Se, which is an n-type impurity, and Zn, which is a p-type impurity, are simultaneously doped into the aInP substrate, the inclined surface portion between the (411) A plane and the (111) plane of the AlGaInP substrate becomes p-type, and (100) The horizontal part along the surface becomes n-type.

This is because in the range where the inclination is larger than the (411) A plane, the rate of incorporation of p-type impurities such as Zn and Mg is large, and conversely, the rate of incorporation of n-type impurities such as Se and S is small. In the vicinity of the (100) plane, the rate of incorporation of n-type impurities such as Se and S increases, and the rate of incorporation of p-type impurities such as Zn and Mg decreases.

In the present invention, instead of growing the selective buried layer as in the prior art, this simultaneous doping is used to remove the n-type current block layers 11 ₁ and 11 ₃ and the p-type current channel layer 11 _2. GaAs current constriction layer 11
Used for the formation of. That is, by co-doping, there are a current blocking layer that blocks the flow of current and a current uniformizing layer that collects p-type carriers flowing from the slope portion on the (100) plane and uniformly supplies them to the p-type cladding layer. If the current confinement layer structure composed of the combination of the above is formed, the contact layer can be continuously grown as it is in the growth device in which the current confinement layer structure is grown. And a contact layer can be formed.

As described above, when the current confinement layer is formed by one-time growth using co-doping, the structure shown in FIG. 1 is formed by putting the semiconductor substrate in and out of the growth apparatus twice. Therefore, the yield is improved and the semiconductor laser device can be realized at low cost, as compared with the conventional growth method which requires the growth device to be taken in and out three times.

[0024]

EXAMPLES Examples of the present invention will be described below. Figure 2
It is a structure explanatory view of the semiconductor laser device of the first embodiment.

In this figure, 1 is an n-GaAs substrate,
2 is an n-GaAs first buffer layer, 3 is n-GaInP
The second buffer layer, 4 is n- (Al _0.7 Ga _0.3 ) _0.5 I
n _{0. 5} P cladding layer, an undoped GaInP active layer 5, 6 _{p- (Al 0.7 Ga 0. 3)} 0.5 In 0.5 P first
Clad layer, 7 is p-GaInP etching stop layer, 8 is p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second
Clad layer, 9 is p- (Al _0.1 Ga _0.9 ) _0.5 In
_0.5 P spike prevention layer, 10 p-GaAs current uniformization layer, 11 Zn / Se co-doped GaAs current confinement layer,
Reference numerals 11 ₁ and 11 ₃ denote n-current blocking layers, 11 ₂ denotes a p-current channel layer, and 12 denotes a p-GaAs contact layer.

The structure of the semiconductor laser device of this embodiment and the method of manufacturing the same will be described with reference to this structure explanatory view.

First step (100) Si-doped n-GaA having a crystal plane on the surface
Se-doped n-GaAs with a thickness of 1 μm on the s substrate 1
First buffer layer 2, 0.1 μm thick Se-doped n-G
aInP second buffer layer 3, a thickness of 1.0 .mu.m Se doped _{n- (Al 0. 7 Ga 0.3)} 0.5 In 0.5 P cladding layer 4, an undoped GaInP active layer 5 having a strain of 0.5% at a thickness of 300Å , 0.2 μm thick Mg-doped p-
_{(Al 0. 7 Ga 0.3) 0.5} In 0.5 P first cladding layer 6, the thickness of 100 Å Mg-doped p-GaInP etching stop layer 7, having a thickness of 0.8 [mu] m Mg-doped p-(A
l _{0. 7} Ga _0.3) semiconductor layer serving as _0.5 an In _0.5 P second cladding layer 8 having a thickness of 0.1 [mu] m Mg-doped p-(Al
_A semiconductor layer to be the _0.1 Ga _0.9 ) _0.5 In _0.5 P spike prevention layer 9, a Zn-doped p-GaAs current equalizing layer 10 having a thickness of 0.5 μm, and a semiconductor layer are sequentially grown by the MOVPE method.

Second Step A stripe-shaped SiO ₂ film is formed on the laminated structure formed in the first step, and the p-GaAs current uniformizing layer 10 is formed by ammonia hydrogen peroxide solution using this SiO ₂ film as a mask. The semiconductor layer to be the above is etched to form a mesa. Then, p- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P Etching is performed up to the middle of the semiconductor layer to be the second cladding layer 8, and finally, the p-GaInP etching stop layer 7 is stop-etched with a hydrochloric acid solution to obtain a p-type as shown in FIG. -(A
l _0.7 Ga _0.3 ) _0.5 In _0.5 P The second cladding layer 8 is formed.

Third step P-GaAs current uniformed by mesa molding in the second step
Layer 10 and p- (Al _0.7Ga_0.3)_0.5In_0.5P number
On top of the 2 clad layer 8, a 1 μm thick Zn / Se simultaneous layer is formed.
The GaAs current confinement layer 11 is formed by the MOVPE method.
Lengthen. This Zn / Se co-doped GaAs current confinement layer
By the growth of 11, n on a plane with (100) plane
-Current blocking layer 11₁, 11₃Is formed, and (11
1) The p-current channel layer 11 is formed on the slope having the A surface.₂But
It is formed. Zn-doped p-G with a thickness of 3 μm
Growth of aAs contact layer 12 in the same MOVPE device
Then, the p-type and n-type metal electrodes are formed, and the laser chip is
By cutting out and bonding to a heat sink
Complete the laser device.

FIG. 3 is an explanatory diagram of a current path of the semiconductor laser device of the first embodiment. The reference numerals used in this figure are the same as those explained with the same reference numerals in FIG. 2, except for the current paths a, b, and c which will be described later. The current path a is an ideal current path, the current path b is a current path due to non-uniform injection, and the current path c is a current path flowing from the simultaneous doped current channel.

In this figure, the current path a is this semiconductor.
Since it is a path that determines the element resistance of the body laser device,
It is necessary for the current to flow as easily as possible. That
Therefore, the p-GaAs current equalizing layer 10 and the p- (Al_0.7G
a_0.3)_0.5In_0.5Spy between the second clad layer 8
P- (Al_0.1Ga_0.9) _0.5In_0.5P
The spike prevention layer 9 is required.

Further, the current path b causes non-uniform current injection into the active layer and deteriorates the stability of the transverse mode of laser oscillation. To prevent this, the p-current channel layer 11 is used. ₂ and p- (Al _0.7 Ga _0.3 ) _0.5 In
The hole barrier between the _0.5 P second cladding layer 8 is large,
It is advantageous if the band spikes. Such conditions are satisfied by the configuration of the first embodiment.

The p-GaAs current equalizing layer 10 is electrically charged.
In order to make the current in the flow path c one uniform current path a
It is provided and p- (Al_0.7Ga_0.3)
_0.5In_0.5The resistance is lower than that of the P second cladding layer 8.
As described above, impurities are introduced at a high concentration. In addition, this p-
The GaAs current equalizing layer 10 has only to have a low resistivity.
-Current blocking layer 11₃It is difficult for current to flow between
Then, the n-current blocking layer 11 ₃And p- (Al_0.1Ga
_0.9)_0.5In_0.5Van in the middle with P spike prevention layer 9
It can also be formed of a semiconductor layer having a gap.
That is, instead of the p-GaAs current equalizing layer 10, an example
For example, GaInP can be used.

In the above embodiments, an example using a specific compound semiconductor material is shown, but the object of the present invention can be achieved and the same effect as the present invention can be obtained by using other compound semiconductor materials. Needless to say.

[0035]

As described above, according to the present invention,
A loss guide type laser device can be realized by continuous growth of the semiconductor layer twice in the MOVPE device, which can be reduced by one time compared with the conventional continuous growth of the semiconductor layer of three times, and dust can be reduced by that amount. Lattice defects due to adhesion can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of AlGaInP-doped plane orientation dependence of Se and Zn.

FIG. 2 is a structural explanatory view of the semiconductor laser device of the first embodiment.

FIG. 3 is an explanatory diagram of a current path of the semiconductor laser device of the first embodiment.

FIG. 4 is a structural explanatory view of a conventional lateral mode control type semiconductor laser device.

[Explanation of symbols]

1 n-GaAs substrate 2 n-GaAs first buffer layer 3 n-GaInP second buffer layer 4 n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 5 undoped GaInP active layer 6 p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first cladding layer 7 p-GaInP etching stop layer 8 p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second cladding layer 9 p- (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P spike prevention layer 10 p -GaAs current homogenizing layer 11 Zn / Se co-doped GaAs current confinement layer 11 ₁ , 11 ₃ n-current blocking layer 11 ₂ p-current channel layer 12 p-GaAs contact layer

Claims (5)

[Claims] 1. An upper p-type clad layer formed in a convex stripe shape on an active layer, and a p-type having a resistivity lower than that of the p-type clad layer formed on a convex stripe of the p-type clad layer. A current equalizing layer, a current confinement layer in which the sloped portion formed on the p-type cladding layer and the current equalization layer is p-type, and the other portion is n-type, and formed on the current confinement layer. And a p-type contact layer. 2. A hetero spike preventing layer is provided between the p type current equalizing layer and the p type cladding layer, and a hetero spike preventing layer is not provided between the slope of the p type cladding layer and the current constricting layer. The semiconductor laser device according to claim 1. 3. The material of the current confinement layer and the material of the current equalization layer are GaAs or GaInP, and the cladding layer is A.
The semiconductor laser device according to claim 1, wherein the semiconductor laser device is lGaInP or AlInP. 4. The substrate is a (100) plane, and the slopes of the p-type clad layer and the current equalizing layer are from (411) A plane to (111) plane.
2. The semiconductor laser device according to claim 1, wherein the current confinement layer, which is located up to the surface A, is formed by simultaneously supplying p-type impurities and n-type impurities. 5. An active layer formed on a (100) plane of a semiconductor substrate, having slopes from (411) A plane to (111) plane.
A step of forming a clad layer made of a convex stripe-shaped p-type semiconductor layer extending up to the A-plane, and a p-type semiconductor layer having a resistivity lower than that of the clad layer on top of the clad layer made of the p-type semiconductor layer And a step of forming a current uniformizing layer consisting of the above, and a slope portion of the clad layer is p-type, and the other part is an n-type current constricting layer on the clad layer and the current uniformizing layer. A method of manufacturing a semiconductor laser device, comprising: a step of simultaneously supplying a type impurity and an n-type impurity; and a step of forming a p-type contact layer on the current confinement layer.