JPH0637394A - Semiconductor laser device and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a ridge-type semiconductor laser device having stable characteristics by a method wherein an optical waveguide having high controllability is formed without etching of a cap layer and an upper cladding layer themselves. CONSTITUTION:A stripe trench is formed in an n-type GaAs layer 14 on a p-type GaAs substrate 13 with high controllability of the trench width by photoelectrochemical selective etching (PEC). After the trench is filled with a p-type AlGaAs cladding layer 4 so as to have a flat surface, the p-type AlGaAs cladding layer 4 is further made to grow to have a required thickness to form an optical waveguide having high controllability.

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 and a method of manufacturing the same, and more particularly to a method of manufacturing a ridge type semiconductor laser.

[0002]

2. Description of the Related Art Currently manufactured semiconductor laser devices have various stripe structures in order to unify the longitudinal and lateral modes and reduce the operating current. Whether or not the stripe structure can be stably formed has a great influence on the characteristics of the semiconductor laser device.

FIG. 2 (d) shows a conventional AlGaAs / Ga of the optical waveguide embedded type, which is a typical shape of the stripe structure.
FIG. 7 is a diagram for explaining a manufacturing method and an operation of the As-based semiconductor laser device.

In the figure, 1 is an n-type GaAs substrate, and an n-type AlGaAs cladding layer 2 is arranged on an n-type GaAs substrate 1. The AlGaAs active layer or the active layer 3 having a quantum well structure is arranged on the n-type AlGaAs cladding layer 2. The p-type AlGaAs cladding layer 4 is arranged on the active layer 3. p-type GaAs cap layer 5
Is formed on the mesa portion of the p-type AlGaAs cladding layer 4. The n-type GaAs block layer 7 is the p-type AlGaAs.
The p-type GaAs contact layer 8 is formed so as to fill both sides of the mesa portion composed of the cladding layer 4 and the p-type GaAs cap layer 5, and the p-type GaAs contact layer 8 is the mesa portion and the n-type GaAs block layer 7.
Formed on. Reference numeral 9 is a p-side electrode, 10 is an n-side electrode, 11 is a current during operation, 12 is an oscillation region, W is a ridge width, and D is an upper clad residual thickness.

Next, a method of manufacturing the conventional semiconductor laser device will be described. First, as shown in FIG. 2A, an n-type GaAs substrate 1, an n-type AlGaAs clad layer 2, an active layer 3, a p-type AlGaAs clad layer 4, and a p-type GaAs are formed.
Crystal growth of the cap layer 5 is performed in order from the bottom (hereinafter referred to as first crystal growth).

Next, as shown in FIG. 2 (b), an insulating film 6 such as a SiNx or SiO2 film is formed, and this is etched using a photoresist (not shown) patterned in the transfer process as a mask. Then, a stripe pattern of the insulating film 6 is formed. Using the stripe pattern of the insulating film 6 as a mask, required portions of the p-type GaAs cap layer 5 and the p-type AlGaAs cladding layer 4 are simultaneously wet-etched with a mixed solution of sulfuric acid, hydrogen peroxide solution and water. At this time, the optical waveguide part is controlled to have a desired ridge width W and upper clad residual thickness D.

Finally, as shown in FIG. 2 (c), the n-type GaAs block layer 7 is buried on both sides of the ridge (hereinafter,
After that, the insulating film 6 is removed by a plasma etcher or HF, and the p-type GaAs contact layer 8 is crystal-grown (hereinafter, referred to as third crystal growth). Then, the p-side electrode 9 is formed on the p-type GaAs contact layer 8 and the n-side electrode 10 is formed on the n-type GaAs substrate 1.

Next, the operation will be described. p-side electrode 9
When a potential difference is applied between the n-side electrode 10 and the n-side electrode 10 by making the p-side positive, a current 11 is generated as shown in FIG. 2 (d). This is because no current flows in the n-type GaAs block layer 7 and the current is narrowed. Then, laser oscillation occurs in the oscillation region 12, which is a portion below the ridge including the active layer 3.

As described above, in the conventional method for manufacturing a ridge type semiconductor laser, the p-type AlGaAs cladding layer 4 and the p-type GaAs cap layer 5 on the active layer 3 are etched,
The optical waveguide portion 12 is formed by forming a stripe-shaped ridge.

[0010]

In the conventional method of manufacturing a ridge type semiconductor laser device, as described above, the cap layer 5 and the cladding layer 4 on the active layer 3 are wet-etched to form an optical waveguide portion formed of a ridge. However, the ridge width W and the upper clad residual thickness D that influence the characteristics of the laser in this wet etching are formed.
Was difficult to control with high precision. Especially, the upper clad residual thickness D among them had a great influence on the laser characteristics even with a slight variation. However, the control of the upper clad residual thickness is p-type AlGaA because of the characteristics of wet etching.
Since it is monitored only by the value obtained by subtracting the etching amount from the crystal thickness of the s-clad layer 4, it is a portion that cannot be actually measured, so control was extremely difficult.

As described above, since the ridge width and the upper clad residual thickness cannot be controlled accurately, one of the characteristics of the laser is reduced.
The beam divergence angle in the horizontal direction, which is one of the
In addition, there is a problem that the life is greatly affected. Moreover, if the cap layer 5 and the clad layer 4 are etched by dry etching instead of wet etching, there is a problem that the active region is damaged by the dry etching.

The present invention has been made to solve the above problems, and an optical waveguide having good controllability is formed by a method different from that of etching the cap layer and the upper cladding layer itself. Thus, it is an object of the present invention to provide a manufacturing method capable of obtaining a semiconductor laser device having stable characteristics, and an object of the present invention is to provide a semiconductor laser device obtained thereby.

[0013]

A method of manufacturing a semiconductor laser device according to the present invention comprises a step of forming an n-type GaAs layer having a desired thickness on a p-type GaAs substrate and photoelectrochemical etching (PEC). A step of selectively removing the n-type GaAs layer with a desired stripe width to form a stripe groove, and embedding a p-type AlGaAs layer in the stripe groove, and then forming the same p-type AlGaAs on the entire surface thereof.
Forming a layer to a desired thickness, and then forming an active layer on the layer,
a step of sequentially forming an n-type AlGaAs layer and an n-type GaAs layer, a step of shaving the p-type GaAs substrate over the entire surface to the same thickness to reduce the total thickness, and a step of forming an electrode. Is included. A semiconductor laser device according to the present invention is manufactured by the above manufacturing method.

[0014]

In the manufacturing method of the present invention, an n-type GaAs layer having a desired thickness is formed on a p-type GaAs substrate, and n-type is formed by photoelectrochemical etching using laser light.
The type GaAs layer is selectively removed with a desired stripe width to form a stripe groove, and a p-type AlG is formed in the stripe groove.
After embedding the aAs layer, an optical waveguide is formed by forming a p-type AlGaAs layer similar to the above on the aAs layer, so that the controllability of the ridge width and the upper clad residual thickness is improved, which is one of the laser characteristics. It is possible to reduce the variation in the beam divergence angle in the horizontal direction.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view from the laser end face side showing a method of manufacturing a semiconductor laser device according to an embodiment of the present invention in the order of steps, and FIG. 3 is a perspective view of the manufactured semiconductor laser. In the figure, 13 is a p-type GaAs substrate and n-type GaAs
The layer 14 is formed on the p-type GaAs substrate 13. An insulating film 6 is formed on the n-type GaAs layer. Arrow 1
Reference numeral 5 indicates photoelectrochemical etching using laser light. Reference numeral 4 is a p-type AlGaAs clad layer formed to be embedded in the etched groove, and reference numeral 3 is the p-type A
An AlGaAs active layer formed on the 1GaAs clad layer 4 or an active layer having a quantum well structure, 2 is an n-type AlGaAs clad layer formed thereon, and 6 is an n-type GaAs contact layer formed thereon. .

Next, a method of manufacturing the semiconductor laser of this embodiment will be described. As shown in Fig. 1 (a), p-type GaAs
The n-type GaAs layer 14 is formed on the substrate 13 to a desired thickness. Next, as shown in FIG. 1 (b), an insulating film 6 is formed on the entire surface of the layer 14, and the stripe-shaped portion of the insulating film 6 having a desired width is masked with a resist patterned by photolithography. Pattern to remove. Using the remaining insulating film 6 as a mask, the wafer in the state of FIG. 1 (b) is immersed in a mixed solution of HCl: H2 O = 1: 20, and the entire wafer is irradiated with laser light 15 from the surface. . When etching using such a laser beam (photoelectrochemical etching: PEC) is performed, an n-type G is formed according to the width of the stripe formed by the insulating film 6.
The aAs current confinement layer 14 is selectively etched away as shown in FIG. 1 (c). This PEC is J. Electroche
m. Soc., Vol.138, No.5, May 1991.

Next, using the insulating film 6 shown in FIG. 1 (e) as a selective growth mask, the p-type AlGaAs cladding layer 4 is flattened to a height equal to the height position of the insulating film 6 as shown in FIG. 1 (d). After the buried growth and removal of the insulating film 6, the p-type AlGaAs clad layer 4 having a desired thickness is formed on the entire surface thereof.
Are grown epitaxially.

Next, as shown in FIG. 1 (e), AlGaA
The s active layer or the active layer 3 having the quantum well structure 3, the n-type AlGaAs cladding layer 2, and the n-type GaAs contact layer 16 are sequentially crystal-grown.

Next, as shown in FIG. 1 (f), p-type GaA
The entire thickness of the p-type GaAs substrate 13 is thinned by polishing or grinding the entire surface from the s-substrate 13 side, and finally, the p-side electrodes 9 and n are provided on the p-type GaAs substrate 13 side.
The semiconductor laser device is manufactured by forming the n-side electrodes 10 on the type GaAs contact layer 16 side, respectively.

The operation of the ridge type semiconductor laser according to the present embodiment is the same as the operation of the conventional ridge type semiconductor laser shown in FIG. 2D, and the current confinement layer 14 causes the current path 11 to consist of the cladding layer 4. The oscillation region 12 formed of the active layer 3 below the ridge oscillates. In this case, the characteristics of the laser are determined by the ridge width W and the clad residual thickness D as described above, but the ridge width W and the clad residual thickness D are formed and controlled by wet etching as in the conventional method in the present manufacturing method. However, the ridge width is patterned by patterning the insulating film 6 by photolithography, and the clad residual thickness D is p-type AlGaAs.
Since it is controlled by the epitaxial growth of the cladding layer 4, it can be controlled with high accuracy, and as a result, a ridge type semiconductor laser having stable characteristics can be obtained.

[0021]

As described above, according to the method of manufacturing a semiconductor laser of the present invention, n-type GaAs having a desired thickness is formed on a p-type GaAs substrate without etching the cap layer and the upper cladding layer itself. Layer is formed and n-type GaAs is formed by photoelectrochemical etching using laser light.
The layer is selectively removed with a desired stripe width to form a stripe groove, and a p-type AlGaAs layer is embedded in the stripe groove, and then a p-type AlGaA layer similar to the above is formed on the upper portion thereof.
By forming the s layer, an optical waveguide having a good controllability of the ridge width W and the clad residual thickness D is formed, so that a semiconductor laser device having stable characteristics can be obtained.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a method of manufacturing a ridge-type semiconductor laser device according to a conventional example in the order of steps.

FIG. 3 is a perspective view of a semiconductor laser manufactured according to an embodiment of the present invention.

[Explanation of symbols]

1 n-type GaAs substrate 2 n-type AlGaAs cladding layer 3 AlGaAs active layer or active layer having a quantum well structure 4 p-type AlGaAs cladding layer 5 p-type GaAs cap layer 6 insulating film 7 n-type GaAs buried block layer 8 p-type GaAs Contact layer 9 p-side electrode 10 n-side electrode 11 current during operation 12 oscillation region W ridge width D upper clad residual thickness 13 p-type GaAs substrate 14 n-type GaAs layer 15 photoelectrochemical etching (PEC) using laser light 16 n-type GaAs contact layer

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor laser device, the step of forming an n-type GaAs layer having a desired thickness on a p-type GaAs substrate, and the n-type G by photoelectrochemical etching.
a step of selectively removing the aAs layer with a desired stripe width to form a stripe groove; and after embedding a p-type AlGaAs layer in the stripe groove,
The same p is formed on the entire surface of the n-type GaAs layer and the n-type GaAs layer
-Type AlGaAs layer is formed to a desired thickness, and an active layer, an n-type AlGaAs layer, and an n-type GaA are formed on the step.
The step of sequentially forming the s layer, the step of cutting the p-type GaAs substrate over the entire surface to the same thickness to reduce the total thickness, and the step of forming the p-type GaAs substrate and the end opposite to the p-type GaAs substrate. n
And a step of forming an electrode on each of the type GaAs layers. 2. A semiconductor laser device manufactured by the manufacturing method according to claim 1.