JPH06177482A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To form a semiconductor laser having self-alignment buried structure by using a P-type semiconductor substrate while growing a crystal once. CONSTITUTION:The surface of a P-type semiconductor substrate 11 is mesa- etched to form a striped mesa 11A, and an N-type InP current constriction layer 13 containing selenium in high concentration is grown on the P-type semiconductor substrate 11, to which the mesa 11A is shaped, and the mesa 11A is self-aligned and buried. Various semiconductor layers required for constituting a semiconductor laser, a P-type InP clad layer 14, an InGaAsP active layer 15, an N-type InP clad layer 16, an N-type InGaAsP contact layer 17, etc., are grown, and an insulating film with an electrode contact window and an N-side electrode and a P-side electrode are formed by applying a normal technique.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of manufacturing a semiconductor laser used as a light source in optical communication or optical network.

In general, a semiconductor laser must have a region for emitting light and a region for confining current, which have completely different functions. Therefore, normally, at least three crystal growths are performed, and However, a process such as masking and etching is also required during its growth, and its complexity leads to a decrease in manufacturing yield and therefore an increase in cost. I won't.

[0003]

2. Description of the Related Art To solve the above problems, it is effective to reduce the number of crystal growths, and various techniques have been reported so far. 2 to 4 show a conventional example in which the number of times of crystal growth is reduced (1
1992 Spring 39th Joint Lecture on Applied Physics 30
a-SF-28 Kondo et al., “1.5 Using MOVPE Method”
5 is a fragmentary front view showing a semiconductor laser in a process key point for explaining "Preparation of 5 .mu.m band self-aligned buried structure laser"), which will be described below with reference to these figures.

See FIG. 2 2- (1) An InGaAsP active layer 2 and a p-type InP clad layer 3 are grown on an n-type InP substrate 1 (first growth). 2- (2) p-type InP clad layer 3, InGaAsP active layer 2, n
A part of the type InP substrate 1 is etched to have a width of, for example, 1.
A mesa portion of 5 [μm] is formed.

See FIG. 3 3- (1) A p-type InP clad layer 4 and an n-type InP current constriction layer 5 containing a high concentration of selenium (Se) as a dopant are grown. InP containing a high concentration of Se has a surface index (10
The n-type InP current confinement layer 5 grows only on both sides of the mesa portion, as shown in the drawing, because the n-type InP current confinement layer 5 has a property that it does not grow in the minute region of the mesa top surface (0).

4- (1) A p-type InP clad layer 6 and a p-type InGaAsP contact layer 7 are formed.

As described above, a structure having a region for light emission and a region for current constriction necessary for a semiconductor laser can be formed by performing crystal growth twice.

[0008]

In the prior art, the reason why the n-type InP current confinement layer 5 can be formed in the self-aligned buried structure as shown is that Se is used as the dopant as described above. It is due to that. Since Se exhibits n-type with respect to InP, it is not possible to obtain the semiconductor laser having the above-mentioned structure in which only the p-type conductivity type is inverted using the p-type InP substrate, and the number of crystal growth is also increased. It is only reduced once compared with the conventional technology.

The present invention makes it possible to form a semiconductor laser having a self-aligned buried structure by using a p-type semiconductor substrate and to perform crystal growth only once.

[0010]

In the present invention, a slight modification is made to the manufacturing process sequence of a semiconductor laser having a self-aligned buried structure so that continuous crystal growth is performed only once on a p-type semiconductor substrate. Basically, it is necessary to obtain a semiconductor crystal layer structure necessary for this type of semiconductor laser.

That is, in the method of manufacturing a semiconductor laser according to the present invention, the surface of a p-type semiconductor substrate (eg, p-type InP substrate 11) is mesa-etched to form stripe mesas (eg, mesa 11A). Then, a semiconductor current confinement layer (for example, an n-type InP current constriction layer 13) containing selenium at a high concentration is grown on the p-type semiconductor substrate having the mesas, and the mesas are self-aligned and embedded. Subsequently, various semiconductor layers including an active layer necessary for constituting a semiconductor laser (for example, p-type InP clad layer 1
4, the InGaAsP active layer 15, the n-type InP cladding layer 16, the n-type InGaAsP contact layer 17, etc.) are grown.

[0012]

By adopting the above means, a semiconductor laser having a self-aligned buried structure can be produced using a p-type semiconductor substrate, and a semiconductor layer necessary for constructing the semiconductor laser can be grown once at a time. Since it can be realized, the manufacturing process can be remarkably simplified, and therefore, it can greatly contribute to the improvement of manufacturing yield and the reduction of cost.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a fragmentary front view showing a semiconductor laser in process steps for explaining one embodiment of the present invention.
Hereinafter, description will be given with reference to this figure. (1) The p-type InP substrate 11 is mesa-etched by applying a resist process and a dry etching method in the lithography technique to have a width of 1 [μm] and a height of 1.5, for example. A mesa 11A having a stripe of [μm] is formed.

(2) Metal-organic vapor deposition
ganic vapor phase epitax
y: MOVPE) method to apply the mesa 11
On p-type InP substrate 11 having A, p-type InP clad layer 12, n-type InP current confinement layer 13, p-type InP clad layer 14, InGaAsP active layer 15, n-type InP clad layer 16, n-type InGaAsP contact layer. Form 17.

Here, the main data regarding each semiconductor layer will be exemplified as follows. For p-type InP substrate 11 Impurity concentration: 1 × 10 ¹⁸ [cm ⁻³ ] For p-type InP clad layer 12 Impurity concentration: 1 × 10 ¹⁸ [cm ⁻³ ] Thickness: 1 μm (top surface of mesa 11A) Regarding the n-type InP current constriction layer 13 Impurity: Se Impurity concentration: 1 × 10 ¹⁹ [cm ⁻³ ] Thickness: 1 [μm] About p-type InP clad layer 14 Impurity concentration: 1 × 10 ¹⁸ [cm ^-3 ] Thickness: 0.5 [μm] InGaAsP active layer 15 Thickness: 0.1 [μm] n-type InP cladding layer 16 Impurity concentration: 1 × 10 ¹⁸ [cm ⁻³ ] Thickness: 2 [ μm] About n-type InGaAsP contact layer 17 Impurity concentration: 3 × 10 ¹⁸ [cm ⁻³ ] Thickness: 0.2 [μm]

(3) Plasma chemical vapor deposition (plasm)
a chemical vapor deposit
ion: P-CVD) method, the insulating film 18 made of SiO _{2 having} a thickness of, for example, 300 [nm] is formed.

(4) By applying a resist process in the lithography technique and a wet etching method using hydrofluoric acid as an etchant, the insulating film 18 made of SiO ₂ is selectively etched to form a stripe pattern. An electrode contact window is formed. In this electrode contact window, of course, the n-type InGaAsP contact layer 17 is formed.
Is partly expressed.

(5) Au having a thickness of, for example, 100 [nm] / 100 [nm] is applied by applying the vacuum deposition method.
An n-side electrode 19 made of Ge / Au is formed.

(6) By applying the vacuum deposition method, the thickness is, for example, 100 [nm] / 100 [nm] / 20.
A p-side electrode 20 made of Au / Zn / Au of 0 [nm] is formed.

As is clear from the above description, the crystal growth required to form the semiconductor laser is required only once.

The present invention is not limited to the above-mentioned embodiments, and many other modifications can be made.

For example, not only the InGaAsP active layer 15 but also an optical guide layer for controlling the refractive index of the InGaAsP active layer 15 may be formed on the n-type InP current confinement layer 13. However, in such a structure, there are cases where the crystal growth is required twice, but in that case, if the present invention is not used, the crystal growth is required once more, so that a total of three times is required. It should be.

[0023]

In the method of manufacturing a semiconductor laser according to the present invention, the surface of the p-type semiconductor substrate is mesa-etched to form stripe mesas, and the p-shaped mesas are formed.
A semiconductor current confinement layer containing a high concentration of selenium is grown on a type semiconductor substrate, the mesa is self-aligned and buried, and then various semiconductor layers including an active layer necessary for forming a semiconductor laser are grown. .

By adopting the above structure, a semiconductor laser having a self-aligned buried structure can be formed using a p-type semiconductor substrate, and a semiconductor layer necessary for forming the semiconductor laser can be formed by one continuous growth. Since it can be realized, the manufacturing process can be remarkably simplified, and therefore, it can greatly contribute to the improvement of manufacturing yield and the reduction of cost.

[Brief description of drawings]

FIG. 1 is a fragmentary front view showing a semiconductor laser in a process essential part for explaining an embodiment of the present invention.

FIG. 2 is a fragmentary front view showing a semiconductor laser in a process key point for explaining a conventional example in which the number of crystal growths is reduced.

FIG. 3 is a fragmentary front view showing a semiconductor laser in a process key point for explaining a conventional example in which the number of crystal growth is reduced.

FIG. 4 is a fragmentary front view showing a semiconductor laser in a process key point for explaining a conventional example in which the number of crystal growth is reduced.

[Explanation of symbols]

 11 p-type InP substrate 11A mesa 12 p-type InP clad layer 13 n-type InP current confinement layer 14 p-type InP clad layer 15 InGaAsP active layer 16 n-type InP clad layer 17 n-type InGaAsP contact layer 18 insulating film 19 n-side electrode 20 p-side electrode

Claims (1)

[Claims] 1. A step of forming a stripe mesa by mesa-etching the surface of a p-type semiconductor substrate, and then, a semiconductor current confinement containing selenium at a high concentration on the p-type semiconductor substrate on which the mesa is formed. Producing a semiconductor laser comprising the steps of growing a layer to self-align the mesas and subsequently growing various semiconductor layers, including the active layers required to form the semiconductor laser. Method.