JPS6242591A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To suppress multiplication of crystal defects and avoid deterioration of a laser and at the same time improve reliability in the high temperature operation by a method wherein not only an impurity which contributes to electric conduction but also an impurity which does not contribute to electric conduction is contained in an active layer which composes a semiconductor laser device. CONSTITUTION:An N-type GaAs blocing layer 2, the first P-type Al0.5Ga0.5As cladding layer 3, a nondoped Al0.1Ga0.9As active layer 4 and the second N-type Al0.5Ga0.5As cladding layer 5 are made to grow on a P-type GaAs substrate 1 by liquid phase epitaxial growth and the whole surface is covered with an N-type GaAs contact layer 6 to compose a semiconductor laser. In this constitution, although the active layer 4 is the nondoped Al0.1Ga0.9As layer, Cu, which has no contribution to electric conduction, is contained in the layer 4 with the concentration of 2X10<-16>/cm<3>. This non-contributing element may be Fe, Ca or the like other than Cu. With this constitution, internal multiplication of crystal defects are minimized and the reliability, especially in high temperature operation, can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor laser device that can be used as a light source for optical information processing devices such as optical fiber communications, optical disks, and laser printers. 2. Description of the Related Art Semiconductor laser devices have become very important as light sources for optical fiber communications, for recording and reproducing optical disk memories, and as devices that form the heart of optical information processing equipment, such as laser printers.

Now, with semiconductor lasers whose applications are being developed one after another in a variety of fields, the demands for improved performance such as reliability, higher output, and shorter wavelengths for l-, , and R are becoming increasingly strict. There is.

Of these, improving reliability is extremely important.

The life of a semiconductor laser is usually predicted by performing a high temperature accelerated life test. Now, the semiconductor laser life 〈τ〉
Assume that there is a dependence as shown in the following equation.

<r>=<r. >exp(Ea/kBT) -----
--(*)kB is Boltzmann's constant, T is absolute temperature, Ea
is activation energy, 4 double, Bee, Jiwois, etc.Applied Physics Letter 28.11,684-68
See p. 6 (1976) (W, B, Ioyce.

start; Appl, Phys, Lett,...
28, 11.

pp, '884-686 (1976)).

By varying T and measuring the lifetime at various temperatures, the activation energy Ea of equation (1) can be determined.

R, L - According to Hartman et al., Ea=
A value of 0.7 eV O is determined. R, L, Hartman, etc. Applied Physics Letter 26.5
, pp. 239-242 (1975) (R, L, Ha
r tmanet, afi, ;Appl, Phys
, Lett, 26, 5, op.

239-242 (1975)).

Usually, the activation energy value is Ea = 0.7 to 0.98
It is said to take a value of about V. From the results of this high temperature accelerated test, the lifespan at room temperature can be estimated by extrapolation.

Now, as can be seen from equation (1), as the operating temperature of a semiconductor laser increases, its lifetime rapidly shortens. Semiconductor lasers do not only operate at room temperature, but often operate at temperatures of 40 to 60° C. when incorporated into devices. For this reason, extending the life when operating at high temperatures is a very important issue.

Here, a buried stripe structure laser (hereinafter referred to as BTRS)
Abbreviated as laser>f, - described as an example. Figure 2 is BTR
This figure shows the structure of an S laser.

1 is a P-type GaAs substrate, 2 is a current blocking layer (contains n-type GaAs), 3 is a first cladding layer (Zn-doped P-type A
fio, 5Gao, sA8), 4 is the active layer (non-doped AIto, 1Gao, 9, is), 5 is the second cladding layer (Te doped n-type AX., 5Ga0.6A)
s layer), 6 is a contact layer (Te doped n-type GaA
s). Figure 3 shows the results of a high temperature accelerated life test of this BTRS laser. This was done in a nitrogen gas atmosphere.
It is operated by constant optical output drive with an optical output of 4.0 mW.

Moreover, the end face is coated with a protective film of 8λ203. No deterioration was observed even after 5000 hours at 60'C, so''C, but deterioration occurred after about 500 hours at 110''C.

Problems to be Solved by the Invention The causes of deterioration of semiconductor lasers include (1) end face oxidation) proliferation of internal crystal defects. Regarding (1), it can be solved by coating the end face with a protective film. In a semiconductor laser device with the above configuration, deterioration is caused by (2)
In a high temperature accelerated life test at 110°C, approximately S
It deteriorates in OO time. As described above, conventional semiconductor laser devices have the disadvantage of low reliability in high temperature operation.

In view of the above drawbacks, the present invention provides a semiconductor laser device that is highly reliable in high temperature operation. Means for Solving the Problems In order to solve the above problems, the semiconductor laser device of the present invention has the following features: It is constructed by including an impurity element other than the doped impurity in the active layer in order to contribute to electrical conduction.

Function: With this configuration, the impurity element suppresses the growth of crystal defects inside the semiconductor laser device, thereby preventing deterioration of the semiconductor laser device, and high reliability can be obtained even in operation at high temperatures.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. A semiconductor laser device according to an embodiment of the present invention has a structure similar to that shown in FIG. 2 for the conventional example, so it will be explained using FIG. 2. Each layer was formed on a P-type GaAt5 substrate 1 by liquid phase epitaxial method. The active layer 4 is a non-doped Aflo, 1Gao, and sAs layer, and the impurity element Cu, which does not contribute to electrical conduction, is included in the crystal at a concentration of 2 x 10"-16crn-'. The following method was used to introduce this concentration into layer 4.The active layer growth solution was Ga1.
A2 is 0.3q for g, and the source Ga for As supply is
A Ga solution was prepared by heating As 0 , 5 , and S+ to 800°C to dissolve A°C and As into a Ga solution. The Ga used at this time had 1 portion of Cu added in advance.
00 ppm was included. Ga1CAj2 and As
An active layer growth solution containing Cu and Iso○°C
By increasing the supersaturation degree by 6°C and using it for active layer growth, the active layer 4 contained 2×10z Cu. In this way, 2×1016 cr of Cu was applied to the active layer 4.
A high temperature accelerated life test was conducted on a semiconductor laser device containing n''-3. The results are shown in Figure 1. This was also conducted under the same conditions as the test in Figure 3. That is, the test was conducted in a nitrogen gas atmosphere. It was performed with a constant optical output drive of 4 mW.The end face was coated with a protective film of A2203.As a result, 60'C, 80'C, 110''G
In either case, no deterioration was observed even after 5000 hours.

Now, if the concentration of Cu in the active layer was 5×10 m or less, the same results as above were obtained. In addition, in the examples, Cu'f: was listed as an impurity element, but it is not limited to this,
Similar results were obtained with Fe and Ca. In addition, although Ga containing an impurity element was used in the example,
Alternatively, a material contained in the source GaAs may be used.

Effects of the Invention As described above, the present invention improves reliability even at high temperatures by including an impurity element that does not contribute to electrical conduction in the active layer, and has great practical effects.

[Brief explanation of the drawing]

1... P-type GaAs substrate, 2-... current blocking layer, 3-... first cladding layer, 4...
Active layer, 5...Second cladding layer, 6...
・Contact layer.

Claims (1)

[Claims] A semiconductor laser device characterized in that an active layer contains an impurity element that does not contribute to electrical conduction.