JPH05283799A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a semiconductor laser device provided with a stripe groove of high accuracy on its GaAs substrate. CONSTITUTION:A stripe crystal growth blocking layer 2 is formed on a GaAs substrate 1, and then an AlGaAs current blocking layer 3 and a melt-back layer 4 are formed therein in this order. Thereafter, the crystal growth blocking layer 2 is removed for the formation of a stripe groove 5, and the a clad layer 6 is formed through an LPE method.

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 used for optical information equipment, optical communication, and a light source for exciting a solid-state laser device.

[0002]

2. Description of the Related Art In recent years, a semiconductor laser device has been widely used as a light source for optical information equipment. As such a semiconductor laser device, for example, JP-A-2-224288 (H01
S 3/18) publication. FIG. 5 shows a manufacturing process diagram of a conventional semiconductor laser device.

First, as shown in FIG. 5A, p-type G
A current blocking layer (n-type GaAs) 52 is formed on the aAs substrate 51 by the LPE method (liquid phase epitaxial method).

Thereafter, as shown in FIG. 5B, a stripe groove 53 is formed in the current blocking layer 52 by wet etching.
To form.

Next, as shown in FIG. 5C, p-type AlGaA is formed on the current blocking layer 52 and in the stripe groove 53.
s clad layer 54, AlGaAs active layer 55, n-type Al
The GaAs cladding layer 56 and the n-type GaAs contact layer 57 are formed in this order by the LPE method.

[0006]

By the way, since the current blocking layer (GaAs) 52 is easily melted back when the p-type cladding layer 54 is formed by the LPE method, the shape of the stripe groove 53 changes. As a result, there are problems that the device characteristics vary and the yield decreases.

To solve this problem, AlGaAs may be used instead of GaAs for the current blocking layer 52. However, in the manufacturing method, the current blocking layer 5 is formed in the step of forming the stripe groove 53 after the formation of the current blocking layer 52.
Since 2 is exposed to the atmosphere and is subjected to a treatment such as washing with water after etching, when the current blocking layer 52 is made of AlGaAs, the surface of the current blocking layer 52 is oxidized. As a result, the p-type cladding layer 54 cannot be formed, or even if it is formed, the p-type cladding layer 54 is formed.
However, there was a problem that the crystallinity of the was deteriorated.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of manufacturing a semiconductor laser device with less variation in characteristics.

[0009]

A method of manufacturing a semiconductor laser device according to the present invention comprises a step of forming a stripe-shaped crystal growth blocking layer on a GaAs substrate and AlGaAs on a GaAs substrate not covered with the blocking layer. Forming a current blocking layer and a meltback layer in this order; removing the crystal growth blocking layer to form a stripe groove exposing the GaAs substrate in a stripe shape; Forming a clad layer in the groove by the LPE method.

Another method of manufacturing a semiconductor laser device according to the present invention comprises the steps of forming a stripe-shaped crystal growth blocking layer on a GaAs substrate and etching the GaAs substrate using the crystal growth blocking layer as a mask. Forming a ridge portion, forming an AlGaAs current blocking layer on the etched and exposed GaAs substrate and a meltback layer on the upper surface thereof, and removing the crystal growth blocking layer to expose the ridge portion A step of forming a stripe groove in the ridge portion, and a step of forming a clad layer in the stripe groove and on the meltback layer by an LPE method,
Consists of.

[0011]

According to the method of manufacturing the semiconductor laser device of the present invention, A
The AlGaAs current blocking layer is oxidized in the atmosphere and the clad layer cannot be crystal-grown on the surface, and even if the crystal growth is possible, the crystallinity is not deteriorated and the AlGaAs current-blocking layer is the LPE. Since the melt-back is less likely to occur in the formation of the cladding layer by the method, the stripe groove can be formed with high accuracy and high yield.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the semiconductor laser device of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a manufacturing process diagram of the semiconductor laser device of this embodiment.

First, as shown in FIG. 1A, the substrate
(P-type GaAs) 1 is prepared and, for example, a film is formed on the substrate 1.
0.5 μm thick SiO₂The film is formed by chemical vapor deposition (CVD
Method), a vapor deposition method, or the like. Next, the SiO₂On the membrane
For example, form a stripe-shaped resist pattern film with a width of 2 μm
Formed by using the resist pattern film as a mask
₂The film is formed, for example, with a hydrofluoric acid-based etching solution (HF + NH_FourF) etc.
By selective etching with₂Consists of
Form a stripe-shaped crystal growth blocking layer 2 having a width of 2 μm
It Then, the resist pattern film is removed.

Next, as shown in FIG. 1B, a current blocking layer (n-type Al _x Ga _{1 -x} ) having a layer thickness of 1.3 μm is formed on the substrate 1.
As: For example, x = 0.1) 3 and a melt back layer (n-type GaAs) 4 having a layer thickness of 0.2 μm in this order in a liquid phase epitaxial method (LPE method) or a metal organic chemical vapor deposition method (M
It is formed (selective growth) by the OCVD method. The crystal growth blocking layer 2 includes a current blocking layer 3 and a meltback layer 4.
Is not formed.

Subsequently, as shown in FIG. 1 (c), the crystal growth inhibiting layer 2 is selectively removed by etching with a hydrofluoric acid-based etching solution to expose the surface of the substrate 1 having a width of 2 μm. The stripe groove 5 is formed.

Thereafter, as shown in FIG. 1D, the first clad layer (p-type A) having a layer thickness of 0.3 μm on the current blocking layer 3 is formed in the stripe groove 5 and on the meltback layer 4.
_{l 0. 45 Ga 0.55 As) 6} , the active layer having a thickness of _{0.07μm (Al 0.14 Ga 0.86 As)} 7, a second cladding layer having a thickness of 2 [mu] m (n-type Al _0.45 Ga _0.55 As) 8, a layer thickness of 3μm The contact layer (n-type GaAs) 9 is continuously grown in this order by the LPE method. The meltback layer 4 is remelted and removed during the growth of the first cladding layer 6.

Although not shown, electrodes are formed on the upper surface of the contact layer 9 and the lower surface of the substrate plate 1, respectively, by a vapor deposition method or the like.

2 (a) and 2 (b), the laser oscillation current in each of 100 semiconductor laser devices manufactured in this embodiment and a semiconductor laser device (GaAs current blocking layer) having a conventional structure manufactured by the conventional manufacturing method. The distribution of thresholds is shown. The semiconductor laser device has a cavity length of 400 μm and R _f
= 8% and R _r = 80%. From this figure, the threshold current is widely distributed as 50 to 70 mA in the conventional manufacturing method, whereas the threshold current is approximately 60 m in the manufacturing method of this embodiment.
It is distributed only in the vicinity of A, and it can be seen that the variation in characteristics is extremely small.

In the method of manufacturing such a semiconductor laser device, since the current blocking layer 3 is not exposed to the atmosphere, there is no possibility that the first cladding layer 6 cannot grow or its crystallinity deteriorates. .. Since the current blocking layer 3 is made of AlGaAs which is difficult to melt back, the stripe groove 5 can be formed with high accuracy.

Since AlGaAs has a larger bandgap than GaAs, light absorption at the end of the current blocking layer 3 on the side of the stripe groove 5 can be reduced, and high output can be achieved.

Next, another embodiment of the semiconductor laser device of the present invention will be described in detail with reference to the drawings. 3 to 4 show manufacturing process diagrams of the semiconductor laser device of this embodiment.

First, as shown in FIG. 3A, Si is formed on the substrate (p-type GaAs) 21 in the same manner as in the first embodiment.
A stripe-shaped crystal growth blocking layer 22 made of O ₂ and having a layer thickness of 0.5 μm and a width of 3 μm is formed.

Next, as shown in FIG. 3B, the substrate 21 is made of, for example, C by using the crystal growth blocking layer 22 as a mask.
Reactive Ion Beam Etching Method Using R ₂ Gas (R
1.5 μm in depth by IBE method) and height 1.5
A ridge portion 23 having a width of 3 μm and a width of 3 μm is formed.

Then, as shown in FIG. 3C, a layer thickness 1. slightly lower than the height of the ridge portion is formed on the exposed surface of the substrate 21 so as to surround the ridge portion 23. A current blocking layer (n-type Al _x Ga _1-x As: for example x = 0.1) 24 having a thickness of 3 μm, and a layer thickness of 0.2 μ on the surface thereof.
The m meltback layer (n-type GaAs) 25 is formed in this order by the LPE method or the MOCVD method. The current blocking layer 24 and the meltback layer 25 are not formed on the crystal growth blocking layer 22.

After that, as shown in FIG. 3D, the crystal growth inhibiting layer 22 is selectively removed by etching with a hydrofluoric acid-based etching solution.

Next, as shown in FIG. 4A, a film thickness of 0.5 μm is formed on the meltback layer 25 and the ridge portion 23.
A SiO ₂ film formed by a CVD method or an evaporation method. Then, on the meltback layer 25 and the ridge portion 23, a width of 0.5 μm inward from the longitudinal end of the ridge portion 23.
A region other than about m, that is, a resist pattern film having a stripe-shaped window having a width of 2 μm is formed. Then, using the resist pattern film as a mask, the SiO ₂ film is selectively removed by etching, for example, with a hydrofluoric acid-based etching solution to form a patterned mask film 26 of SiO ₂ . At this time, the ridge portion 23 is exposed.

Then, as shown in FIG. 4B, RIBE is formed on the ridge portion 23 using the mask film 26 as a mask.
1.5μm depth and width 2μ
The groove 27 of m is formed. At this time, a melt back layer 28 having a width of 0.5 μm is formed on the side surface of the groove 27.

Then, as shown in FIG. 4C, the mask film 26 is selectively removed by etching with a hydrofluoric acid-based etching solution. A resist film may be used as the mask film 26.

Then, as shown in FIG. 4D, a first clad layer (p-type Al _0.45 Ga _0.55 As) 29 having a layer thickness of 0.3 μm and a layer thickness of 0 are formed in the groove 27 and on the meltback layer 25. 0.07 μm active layer (Al _0.14 Ga _0.86 As) 30,
The second clad layer (n-type Al _0.45 Ga _0.55 A with a layer thickness of 2 μm)
s) 31, contact layer (n-type GaAs) with a layer thickness of 3 μm
32 is crystal-grown in this order by the LPE method. still,
The meltback layers 25 and 28 are remelted and removed during the growth of the first cladding layer 29.

Although not shown, electrodes are formed on the upper surface of the contact layer 32 and the lower surface of the substrate 21 by a vapor deposition method or the like.

The semiconductor laser device according to this embodiment is also shown in FIG.
Similar to (a), there was little variation in distribution.

Also in the method of manufacturing such a semiconductor laser device, since the current blocking layer 24 is not exposed to the atmosphere, there is no fear that the first cladding layer 29 cannot grow or its crystallinity deteriorates. .. Since the current blocking layer 24 is made of AlGaAs, which is hard to be melted back, the stripe groove 27 can be formed with high accuracy, which is the same effect as in the first embodiment.

In the first and second embodiments described above, the SiO ₂ film was used as the crystal growth blocking layer, but the surface was oxidized and the Al _y Ga _1-y As (for example 0.2 ≤ y ≤
1, preferably 0.8 ≦ y ≦ 1) film. However, in this case, it is necessary to use, for example, an iodine-based etching solution as the etching solution, and it is necessary to use the LPE method for forming the AlGaAs current blocking layer and the meltback layer on the upper surface thereof. Further, Si ₃ N ₄ or the like can be used as the crystal growth blocking layer.

GaAs may be used as the active layer. Further, an n-type GaAs substrate may be used, and in this case, it is necessary to make the clad layer and the like have a conductivity type opposite to that of the above embodiment.

[0035]

According to the method of manufacturing the semiconductor laser device of the present invention, the AlGaAs current blocking layer is oxidized in the atmosphere and the clad layer cannot be crystal-grown on the surface of the AlGaAs current blocking layer. Since the AlGaAs current blocking layer is less likely to be melted back during the formation of the cladding layer by the LPE method, the stripe groove can be formed with high accuracy and high yield.
Therefore, it is possible to provide a semiconductor laser device with less variation in characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a step in a method for manufacturing a semiconductor laser device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a characteristic distribution of a semiconductor laser device manufactured by a method of manufacturing a semiconductor laser device according to the present invention and a characteristic distribution of a semiconductor laser device manufactured by a method of manufacturing a conventional semiconductor laser device.

FIG. 3 is a sectional view showing a step in a method for manufacturing a semiconductor laser device according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a step that follows the step in FIG. 3 of the method for manufacturing the semiconductor laser device according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the steps of a conventional method for manufacturing a semiconductor laser device.

[Explanation of symbols]

 1 GaAs Substrate 2 Crystal Growth Blocking Layer 3 AlGaAs Current Blocking Layer 4 Meltback Layer 5 Stripe Groove 6 Cladding Layer 21 GaAs Substrate 23 Ridge 24 AlGaAs Current Blocking Layer 25 Meltback Layer 27 Stripe Groove 29 Cladding Layer

Claims (2)

[Claims] 1. A step of forming a stripe-shaped crystal growth blocking layer on a GaAs substrate, and a step of forming an AlGaAs current blocking layer and a meltback layer in this order on a GaAs substrate not covered by this blocking layer, From the step of removing the crystal growth inhibiting layer to form a stripe groove exposing the GaAs substrate in a stripe shape, and the step of forming a clad layer on the meltback layer and in the stripe groove by the LPE method. Of manufacturing a semiconductor laser device. 2. A step of forming a stripe-shaped crystal growth blocking layer on a GaAs substrate, a step of etching the GaAs substrate using the crystal growth blocking layer as a mask to form a ridge portion, and the step of etching and exposing. GaA
s a step of forming an AlGaAs current blocking layer on the substrate and a meltback layer on its upper surface, a step of removing the crystal growth blocking layer to expose a ridge portion, and a step of forming a stripe groove in the ridge portion, And a step of forming a clad layer in the stripe groove and on the meltback layer by the LPE method.