JPH06244497A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To keep a clad layer having a specified thickness by the thin etching stopper layers of a semiconductor laser device. CONSTITUTION:The title semiconductor laser device has an etching stopper region 22 formed on a clad layer 6, block layers 8 formed on the etching stopper region 22, a ridge-shaped clad layer provided between the block layers 8, and a contact layer 9 formed on the clad layer. The etching stopper region 22 has a plurality of etching stopper layers 26 and interposing layers 27 arranged interchangeably with the etching stopper layers 26. Consequently, it becomes possible to keep the clad layer 6 having a specified thickness, and the photoabsorption of the etching stopper layers is also difficult to occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device, and more particularly to a semiconductor laser device which can obtain uniform laser characteristics.

[0002]

2. Description of the Related Art For example, JP-A-63-31488
As disclosed in Japanese Patent Laid-Open No. 3 (1994), a semiconductor laser device having an active layer made of GaInP and a cladding layer made of AlGaInP formed on the upper and lower parts of the active layer is known. For example, as shown in FIG. 4, a conventional semiconductor laser device (1) includes an n-type GaAs substrate (2) and an n-type GaAs buffer layer formed on the n-type GaAs substrate (2). (3), a clad layer (4) made of n-type AlGaInP, an active layer (5) made of GaInP, and a clad layer (6) made of P-type AlGaInP formed on the active layer (5). An etching stopper layer (7) made of GaInP formed above the cladding layer (6), a block layer (8) made of n-type GaAs, and a contact layer (9) made of p-type GaAs. I have it. A ridge-shaped clad layer (waveguide layer) (10) is provided between the block layers (8) to form a so-called ridge-type waveguide structure. Above the clad layer (10) is a stopper layer (waveguide layer). A contact layer (11) made of GaInP having the same composition as 7) is formed. Lower surface of GaAs substrate (2) and contact layer (9)
The electrode layers (12) and (13) are formed on the respective upper surfaces of the.

During manufacturing, selective etching is performed using an etching solution having an etching rate sufficiently higher than that of the etching stopper layer (7) for the cladding layers (6) and (10).

The etching stopper layer (7) formed between the clad layer (6) formed on the active layer (5) and the ridge-shaped clad layer (10) has a function of suppressing excessive etching. Therefore, according to this manufacturing method, there is an advantage that the layer thickness of the clad layer (6), which affects the laser characteristics, does not become non-uniform for each etching process.

[0005]

By the way, in the semiconductor laser of FIG. 4, the etching stopper layer (7) is formed above the ridge-shaped clad layer (10) for reasons such as reduction of contact resistance with respect to the contact layer (9). GaIn with the same composition as
A contact layer (11) made of P is formed. Since the contact layer (11) formed of an ultrathin film has a relatively large stopper action against etching, the layer thickness of the etching stopper layer (7) is set to a thickness corresponding to the error in the etching process. It

However, when the etching stopper layer (7) made of the same compound semiconductor material as that of the active layer (5) is formed to be thick, the light emitted from the active layer (5) is absorbed by the etching stopper layer (7) and the light is emitted. Attenuating action occurs, and defects such as an increase in the threshold current of the laser and a decrease in the life characteristics become conspicuous.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a semiconductor laser device in which an etching process for forming a waveguide layer can be performed satisfactorily and satisfactorily, and light absorption by an etching stopper layer hardly occurs.

[0008]

In a semiconductor laser device according to the present invention, a first conductivity type clad layer, an etching stopper region, and a second conductivity type current block layer are sequentially laminated on an active layer. And a ridge-shaped waveguide layer is arranged between the current blocking layers. The etching stopper area is
A plurality of ultra-thin etching stopper layers having a thickness of 100 angstroms or less and made of a compound semiconductor different from the compound semiconductor forming the cladding layer, and a compound semiconductor arranged between the etching stopper layers and forming the etching stopper layer are different from each other. And an intervening layer made of a compound semiconductor. The clad layer and the intervening layer are made of AlGaInP, and the etching stopper layer is made of GaInP.

[0009]

The etching stopper region having a plurality of etching stopper layers produces a desired etching stopping action.
Further, since the thickness of each layer of the etching stopper layer is thin, a quantization level is formed and the absorption edge is cisted to the high energy side, so that the light absorption action by the etching stopper layer is unlikely to occur.

[0010]

EXAMPLE An example of the present invention applied to a semiconductor laser device will be described with reference to FIGS. 1 to 3, the same parts as those shown in FIG. 4 are designated by the same reference numerals.

FIG. 1 is a sectional view of a semiconductor laser device (20) according to this embodiment. To manufacture the semiconductor laser device (20), first, the semiconductor substrate (21) shown in FIG. 2 is prepared. The semiconductor substrate (21) is a metal organic vapor phase epitaxy (MOV
It has a multilayer structure formed on an n-type GaAs substrate (2) by PE method). This multilayer structure comprises a buffer layer (3) composed of n-type GaAs formed on an n-type GaAs substrate (2) and an n-type (Al _0.5 Ga _0.5 ) _0.5 I.
A cladding layer (4) made of n _0.5 P and undoped Ga _0.5
Active layer made of In _0.5 P and (5), the P-type (Al _{0. 5} Ga
_0.5 ) _0.5 In _0.5 P cladding layer (6), etching stopper region (22), P type (Al _0.5 Ga _0.5 )
_A cladding layer (23) made of _0.5 In _0.5 P, a contact layer (24) made of P-type GaInP, and a P-type GaAs.
And a contact layer (25) composed of The etching stopper region (22) has a thickness of about 150.
Angstrom P type (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P
The intervening layer (26) consisting of an etching stopper layer made of Ga _0.5 In _{0. 5} P ultrathin about 40 Angstroms thick and (27) is formed by alternately stacking.

Next, an etching mask (not shown) made of a SiO ₂ film or the like is selectively formed on the upper surface of the contact layer (25), and an etching solution of sulfuric acid: hydrogen peroxide: water is 1: 1: 50. The contact layer (25) is further mesa-etched with concentrated sulfuric acid at 60 ° C. to selectively mesa-etch the contact layer (24) and the clad forming layer (23), and the ridge-shaped clad layer (waveguide layer) shown in FIG. 28) is formed. Here, the etching rate of Ga _0.5 In _0.5 P with respect to the concentrated sulfuric acid etching solution is about 0.04 micrometer per minute. On the other hand, the etching rate of the _{(Al 0.5 Ga 0.5) 0.5 In} 0. 5 P with respect to the etching solution is approximately 0.4 micrometers per minute,
It is about 10 times higher than the etching rate of Ga _0.5 In _0.5 P. For this reason, the etching stopper layer (27) is extremely thin, but the etching stopper region (22) has a plurality of GaInP layers.
Since it contains a layer, it functions well as an etching stopper and functions as a thick Ga _0.5 In _0.5 P etching stopper. Therefore, in consideration of an etching error, that is, an error in controlling the etching rate and the etching time, at least one layer of the plurality of second stopper layers (27) is left at the time of etching even when the etching proceeds to the maximum. The thickness of the cladding layer (6) arranged above the active layer (5) can be maintained in the existing state.

Conventionally, an etching stopper layer made of Ga _0.5 In _0.5 P is formed to have a sufficient thickness to cope with variations in the amount of etching, and the lower region is left thin to prevent etching of the lower cladding layer. The etching process had to be performed while monitoring so that the work was complicated. However, in this embodiment, Ga _0.5 In _0.5
Since each layer of the ultrathin stopper layer made of P hardly absorbs light, the etching step can be performed without paying close attention to the thickness of the remaining etching stopper layer as in the conventional case. Therefore, the process becomes extremely easy and the yield is improved.

In this embodiment, as shown in FIG. 3, two etching stopper layers (26) are provided above the cladding layer (6).
Remains. For convenience of description, the etching stopper layer (26) and the intervening layer (27) are shown as thick, but these etching layers are actually sufficiently thinner than the cladding layer (6).

Next, using an etching mask (not shown) above the ridge-like cladding layer (28) as a selective mask, n on both sides of the ridge-like cladding layer (28) by selective MOVPE.
A current blocking layer (8) of GaAs type is formed, and after removing the selective mask, a contact layer (9) of P type GaAs is formed. The electrode layers (12) and (13) are formed on the upper surface and the lower surface of the obtained semiconductor laser chip, and FIG.
The element shown in is completed. The etching stopper layer (2
For 6), it is desirable that the thickness is 100 angstroms or less so that light absorption is unlikely to occur.

[0016]

According to the semiconductor laser device of the present invention, light absorption by the etching stopper layer is unlikely to occur, and defects such as an increase in the threshold current of the laser and a decrease in life characteristics do not occur. In addition, the etching process can be easily performed and the yield is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention applied to a semiconductor laser device.

FIG. 2 is a sectional view of a semiconductor substrate used for manufacturing a semiconductor laser device.

3 is a cross-sectional view showing a state where the semiconductor substrate of FIG. 2 is mesa-etched.

FIG. 4 is a sectional view of a conventional semiconductor laser device.

[Explanation of symbols]

(2) ・ ・ ・ GaAs substrate, (6) ・ ・ ・ Clad layer, (8)
... Block layer, (21) ... Semiconductor substrate, (22).
..Etching stopper region, (24) ... contact layer, (25) ... contact layer, (26) ... intervening layer,
(27) .. Etching stopper layer, (28) ... ridge clad layer,

Claims (2)

[Claims] 1. A clad layer of a first conductivity type, an etching stopper region, and a current block layer of a second conductivity type are sequentially stacked on the active layer, and a ridge-shaped conductor is formed between the current block layers. In a semiconductor laser device having a wave layer, the etching stopper region includes a plurality of ultra-thin etching stopper layers having a thickness of 100 angstroms or less and made of a compound semiconductor different from the compound semiconductor forming the cladding layer, A semiconductor laser device comprising: an intervening layer made of a compound semiconductor different from the compound semiconductor forming the etching stopper layer and arranged between the etching stopper layers. 2. The cladding layer and the intervening layer are made of AlGaIn.
The ultra-thin etching stopper layer is made of GaInP.
The semiconductor laser device according to claim 1, comprising: