JPS6286785A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To improve reliability in high temperature operation by making clad layers contain impurity element which has a deep level not contributing to electrical conduction. CONSTITUTION:Impurity element which has a deep level not contributing to electrical conduction is contained in a clad layer. For instance, an N-type GaAs current blocking layer 2, the Zn doped P-type Al0.5Ga0.5As 1st clad layer 3, a nondoped Al0.1Ga0.9As active layer 4, the Te doped N-type Al0.5Ga0.5As 2nd clad layer 5 and a Te doped N-type GaAs contact layer 6 are formed on a P-type GaAs substrate 1. Impurity element Cu, which does not contribute to electrical conduction, is contained in the 1st and 2nd cladding layers 3 and 5 with concentration of 2X10<16>cm<-3>. With this constitution, multiplication of crystal defects growth in the semiconductor laser is suppressed by the impurity element and deterioration of the semiconductor laser can be avoided so that, even in the operation at high temperature, high reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention 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.

BACKGROUND OF THE INVENTION In recent years, semiconductor laser devices have become extremely 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. There is.

Now, as described above, semiconductor lasers are being used one after another in various fields, and demands for improved performance such as reliability, higher output, and shorter wavelength are becoming increasingly strict.

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 lifespan of semiconductor lasers is
> has the dependence shown by the following equation.

< r > = < r () > e x p (E
a /kB T )kB is the Boltzian constant, T is the absolute temperature, and Ea is the activation energy. For example, see W.B.Joyce Applied Fixtures Letters 28, 11°684-686 (1976) (W.
B. Joyae.

et al; Appl, Phys, Lett, 2
8.11, pp.

684-686 (1976)).

By changing T and measuring the lifetime at various temperatures, the activation energy Ea of equation (1) can be determined by changing T. R.L. Hartman (R.I.).

According to Hartman et al., Ea == 0.7
The value of eV has been determined. R.L. Hartman et al. Applied Fixtures Letters 26, 5, 23
9-242 (1975) (R,L, Hartman
, et an; Appl, Phys, Lett.

26.5. pp, 239-242 (1975)) Usually, the value of activation energy is Ea==0.7-0.9e
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 necessarily operate only 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") will be described as an example.

FIG. 3 shows the structure of a BTRS laser. 1
is a p-type GaAs substrate, 2 is a current blocking layer (
n-type GaAs), 3 is the first cladding layer (Zn-doped p-type An., 5Ga, 6As), 4 is the active layer (non-doped AI!,., 1Gao, 9As), s is the second cladding layer (Te-doped n Type AA., 6G ao
, 6A s layer), and 6 is a contact layer (To doped n-type GaAs). FIG. 4 is a characteristic diagram showing the results of a high temperature accelerated life test of a BTRS laser. This was carried out in a nitrogen gas atmosphere, and was driven with a constant optical output of 4.0 mW. Also, AI on the edge! , 2o3 protective film is coated. No deterioration was observed even after 5,000 hours at 60'C and 80°C, but at 110'C, about 5% deterioration was observed.
It will deteriorate in 00 hours.

Problems to be Solved by the Invention The causes of deterioration of semiconductor lasers include: 1) Edge oxidation 2) Multiplication of internal crystal defects. 1 can be solved by coating the end face with a protective film. In a semiconductor laser device having the above configuration, deterioration progresses due to cause 2 of deterioration, and in a high temperature accelerated life test at 110'C, deterioration occurs in approximately SOO time, and the reliability of high temperature operation is low. was.

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 includes a deep level impurity element other than the impurity doped in order to contribute to electrical conduction in the cladding layer.
It consists of a stand of 16 cm-' or less.

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. The structural diagram of a semiconductor laser shown in FIG. 3 is similar to the structure of a semiconductor laser device according to an embodiment of the present invention, so the description will be made with reference to the same figure.

Each layer was formed on a p-type GaAs substrate 1 by a liquid phase epitaxial method. The first cladding layer 3 contains p-type for 1°s
The first cladding layer 3 contains an impurity element Cu, which does not contribute to electrical conduction, at a concentration of 2 x 10-16 cm-' in the crystal.

The following method was used to introduce Cu into the first cladding layer 3 to this concentration. The solution for growing the first cladding layer was 2.6m9 of 82 for Ga1y, e of Zn, oIR9 and Noah-y for supplying A8, and GaAs+.
By heating 0.57 and 8oo'C, A
1, Zn, and A8 were dissolved in a Ga solution.

The Ga used at this time had 100% Cu added in advance.
ppm was included. Ga IICA II (!:
By using the first cladding layer solution in which Zn, As, and Cu are dissolved at a supersaturation level of 6°C from 800'C to grow the first cladding layer, the first cladding layer contains C.
2×10 16 crn-3 u were included. Similarly, the second
The cladding layer 5 also contained 2 x 1016 cm-' of Cu. In this manner, a high temperature accelerated life test was conducted on a semiconductor laser device in which 2×1016 crn-3 of Cu was contained in the first cladding layer and the second cladding layer. The results are shown in FIG. This was also conducted under the same conditions as the test shown in FIG. That is, the test was conducted in a nitrogen gas atmosphere, and the optical output was 4rnW.
This is done using a constant optical output drive. Also, the end face is A12o
It is coated with a protective film of No. 3. As a result, 60°
No deterioration was observed after 6000 hours at either 980°C or 110°C.

Now, if the concentration of Cu in the cladding layer was 5×10 cIn or less, the same results as above were obtained. This is shown in FIG. Further, in the examples, Cu was used as an impurity element, but the impurity element is not limited to this, and similar results were obtained with Fe and Ca. Further, in the embodiment, an impurity element containing GaK was used, but it is also possible to use an impurity element containing GaK, dolbant, or source GaAs.

Effects of the Invention As described above, in the present invention, when the cladding layer contains an impurity element that does not contribute to electrical conduction, reliability is improved even at high temperatures, and its practical effects and effects are great. There is something.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing the results of a high temperature accelerated life test in an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the results of a high temperature accelerated life test when the impurity concentration is changed, and Fig. 3 is a characteristic diagram showing the results of a high temperature accelerated life test in an example of the present invention.
FIG. 4, which is a structural diagram of the RS laser, is a characteristic diagram showing the results of a conventional high temperature accelerated life test. DESCRIPTION OF SYMBOLS 1... p-type GaAs substrate, 2... current blocking layer, 3... first cladding layer, 4...
...Active layer, 6...Second cladding layer, 6
...Contact layer. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure movement interval (-) Figure 2 Figure 4 movement (-9

Claims (1)

[Claims] A semiconductor laser device characterized in that a cladding layer contains a deep level impurity element that does not contribute to electrical conduction.