JPH06296062A - Visible light semiconductor laser device - Google Patents

Abstract

PURPOSE:To provide an AlGaInP semiconductor laser device which is small in variation of oscillation threshold current and excellent in manufacturing yield. CONSTITUTION:A visible light semiconductor laser device is equipped with a GaAs substrate 11 and AlGaInP semiconductor layers besides an active layer formed on the primary surface of the GaAs substrate 11, and a face tilted by an angle of over 5 deg. in a [011] direction from a (100) face is made to serve as a primary surface of the GaAs substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AlGaInP (aluminum-gallium-indium-phosphorus) based visible light semiconductor laser device.

[0002]

2. Description of the Related Art MOCVD (metal organic chemical vapor deposition) is one effective method for growing GaInP crystals. However, many crystal defects are often observed in the GaInP crystal grown by this method. For example, when a GaInP crystal is grown by MOCVD on a GaAs (gallium arsenide) substrate having a (100) surface as a surface, a crystal defect consisting of a hillock having an elliptic cross section in the growth surface has a crystal defect of 1 cm ^2. About 6,000 pieces are generated.

Journal of Crystal Gro as prior art
wth, 17 (1972), 189-206, when growing GaAs on a GaAs substrate by the CVD method, the plane orientation of the substrate is inclined from the (100) plane to the [110] direction by 2 ° to 5 °. It is described that the use of the above-mentioned one can greatly reduce the generation of undesired pyramidal hillocks on the surface of the grown crystal.

In addition, Journal of Crystal Growth, 68
(1984), 483-489, describes an AlGaInP-based semiconductor laser device manufactured by using the MOCVD method. The structure is shown in FIG.

In the figure, (21) is a substrate made of n-type GaAs, and one main surface (21a) thereof has a surface inclined by 2 ° from the (100) surface in the [110] direction.

Reference numeral (22) denotes one main surface (21) of the substrate (21).
a) a buffer layer made of n-type GaAs having a thickness of 0.7 μm deposited on the buffer layer, and (23) an n-type (Al _0.3 Ga _0.7 ) layer having a thickness of 1.4 μm deposited on the buffer layer (22).
_An n-type clad layer made of _0.5 In _0.5 P, (24)
An active layer made of AND-Ga 0 _.5 In 0 _.5 P laminated on the mold clad layer (23) to a thickness of 0.23 μm, (2
5) is a p-type clad layer composed of p-type (Al _0.3 Ga _0.7 ) _0.5 In _0.5 P laminated on the active layer (24) to a thickness of 1.4 μm, and (26) is the p-type clad layer (25) It is a cap layer made of p-type GaAs, which is stacked on top of this with a thickness of 1.0 μm.

(27) is a block layer made of SiO ₂ laminated on the cap layer (26), and has stripe grooves (2 with a width of 20 to 23 μm reaching the cap layer (26).
8). (29) is an exposed cap layer (26)
A p-type electrode composed of an Au / Zn electrode, in which a Zn film and an Au film are deposited in this order on the upper layer and the block layer (27), (3
0) is Ni on the other main surface (21b) of the substrate (21).
Film / Ge film / Au film deposited in this order on Au / Ge /
It is an n-type electrode made of a Ni electrode.

[0008]

[Problems to be Solved by the Invention] Such Journal of Cryst
In the conventional device described in al Growth, 68 (1984), 483-489, there is a problem in that the variation in the oscillation threshold current of each manufactured device is large and the manufacturing yield is low.

Therefore, when the present inventors examined the surface of the uppermost cap layer after stacking each semiconductor layer in such a conventional device, many crystal defects (hillocks) were observed.

That is, Journal of Crystal Growth, 17
(1972), 189-206, the growth surface of the GaAs substrate is 2 ° in the [110] direction from the (100) plane.
The use of a surface inclined by ~ 5 ° makes Ga by the CVD method
It is effective in the growth of As crystals and not in the growth of AlGaInP-based semiconductor crystals by the MOCVD method.

Therefore, the present invention provides an AlGaInP-based semiconductor laser device having a small variation in the oscillation threshold current for each manufactured device and a high manufacturing yield.

[0012]

The device of the present invention is (10)
A GaAs substrate whose main surface is a surface inclined by 5 ° or more in the [011] direction from the (0) plane, and an AlGaInP-based semiconductor layer including an active layer formed on the main surface. .

In the device of the present invention, the main surface is the surface inclined by 5 ° or more in the [011] direction from the (100) surface.
A conductive type GaAs substrate, a first conductive type AlGaInP clad layer formed on the main surface, an active layer formed on the clad layer, and a second conductive type second layer formed on the active layer. And an AlGaInP clad layer.

Further, in the device of the present invention, the main surface is a surface inclined by 5 ° or more in the [011] direction from the (100) surface.
An As substrate, a semiconductor layer in which the generation of crystal defects in the initial growth process due to the inclination in the above direction is suppressed by being deposited on the main surface, and an active layer formed on the semiconductor layer are formed. And an AlGaInP-based semiconductor layer containing the same.

Further, the device of the present invention has a Ga main surface having a surface inclined by 5 ° or more in the [011] direction from the (100) surface.
An As substrate, a semiconductor layer deposited on the main surface in which generation of crystal defects is suppressed, and an AlGaInP-based semiconductor layer including an active layer formed on the semiconductor layer are provided. And

In particular, the active layer is made of GaInP.

Further, in the device of the present invention, a main surface is a surface inclined by 5 ° or more from the (100) surface in the [011] direction.
It is characterized by comprising an As substrate and an active layer made of GaInP formed on the main surface and generating oscillated light whose wavelength is shortened due to the inclination in the above direction.

Further, in the device of the present invention, the main surface is a surface inclined by 5 ° or more in the [011] direction from the (100) surface.
An As substrate and a G formed on the main surface, in which the emission energy of photoluminescence increases due to the inclination in the above direction G
and an active layer made of aInP.

Further, in the device of the present invention, the main surface is a Ga having a surface inclined by 5 ° or more in the [011] direction from the (100) surface
An As substrate, and an AlGaInP-based semiconductor layer including an active layer made of GaInP, which is formed on the main surface and generates oscillation light whose wavelength is shortened due to the inclination in the above direction, are provided.

Further, the device of the present invention has a Ga main surface having a plane inclined by 5 ° or more in the [011] direction from the (100) plane.
An As substrate and a G formed on the main surface, in which the emission energy of photoluminescence increases due to the inclination in the above direction G
and an AlGaInP-based semiconductor layer including an active layer made of aInP.

In particular, the inclined surface is a surface inclined by 5 ° to 7 °.

Further, the inclined surface is a polished surface.

[0023]

According to the present invention, by the action of the substrate crystal growth surface tilted in a specific direction, the generation of Ga droplets, which causes hillocks which are crystal defects, can be significantly reduced at the initial stage of growth, and the substrate can be significantly reduced. A formed above
Each of the 1GaInP-based semiconductor layers is formed with good crystallinity.

Further, due to the action of the substrate crystal growth surface tilted in a specific direction, the emission energy of the photoluminescence of GaInP becomes large. That is, when the active layer is made of GaInP, the wavelength of oscillation light can be shortened.

[0025]

1 is a block diagram of an apparatus for manufacturing a semiconductor laser device according to the present invention. This device itself is well known, and the GaAs substrate (1) is fixed on the susceptor (3) in the reaction vessel (2). The susceptor (3) is rotationally driven at a speed of 8 to 10 rpm during growth. The running water channel (4) is in close contact with the outer wall of the container (2) to cool the container (2), while the RF coil (5) surrounding the container (2) enables heating of the susceptor (3). The container (2) is evacuated by the action of the rotary pump (7) through the filter (6). The reaction gas generated in the container (2) is generated by the TMGa (trimethylgallium) liquid tank (8) and the TMIn (trimethylindium) liquid tank (9).
To H ₂ (hydrogen gas) through the constant flow rate device (10) and bubbling. PH ₃ (phosphine) and H ₂ as other reaction gas and carrier gas are appropriately introduced into the reaction vessel (2) through the constant flow rate device (10).

In such an apparatus, the temperature of the substrate (1) is set to 6
Hold at 40 ℃, PH ₃ gas / (TMGa gas + TMI
n gas) = about 500 and each gas is introduced into the container (2), and the pressure inside the container is maintained at 70 Torr by the low pressure MOCVD method to form InGaP having a thickness of about 1.2 μm.
Crystal growth was performed. As is well known, at the time of heating the substrate before the start of growth, it is preferable to flow arsine gas to prevent As from escaping from the substrate.

At the time of the above-mentioned growth, the measurement result of the crystal defect (hillock) density (the number of hillocks per 1 cm ² ) with respect to the grown crystal when various substrate plane orientations are selected, and the photo by the argon laser (wavelength about 5145Å) excitation The luminescence measurement results are shown in the table below.

[0028]

[Table 1]

From these measurement results, it can be seen that according to this example, an InGaP crystal having very few defects and good crystallinity can be obtained.

It is also found that the larger the angle in the [011] direction from the (100) plane, the greater the emission energy of the GaInP crystal. That is, from the (100) plane, [01
1] the active layer using a plane inclined by 5 ° or more in the direction
In the case of a semiconductor laser device made of nP, the oscillation wavelength can be shortened.

In this embodiment, the growth conditions can be changed as appropriate, and for example, the growth temperature is suitable in the range of 620 ° C to 670 ° C. However, from the (100) plane of the substrate plane orientation, [01
1] direction has an inclination angle of 5 ° or more, preferably 5 ° to 7 °
Must be set in the range of 1 or otherwise, a sufficient effect for reducing the crystal defect density cannot be obtained.

The present method can be effectively applied not only to the growth of InGaP crystals but also to the growth of InGaAlP crystals containing a small amount of Al.

As described above, GaI is formed on the GaAs substrate.
When growing an nP crystal or an AlGaInP crystal, it is preferable that the substrate be tilted in the plane orientation from the (100) plane to the [011] direction by 5 ° or more.

Since a high quality InGaP crystal or InGaAlP crystal can be produced by this method, a double heterojunction laser diode using such a crystal can be realized. FIG. 2 shows an example thereof.

In the figure, (11) is a carrier concentration of 2 ×
This is a substrate of 10 ¹⁸ cm ^{−3 made} of n-type GaAs, and one main surface (11a) thereof is inclined by 5 ° or more, for example, 5 ° in the [011] direction from the (100) surface by polishing.

(12) is a buffer layer, (13) is an n-type clad layer, (14) is an active layer, (15) is a p-type clad layer, and (16) is a cap layer.
20 to 670 ° C., for example 670 ° C., reaction chamber pressure 70 Torr
Using the low pressure MOCVD method of (1), the layers are sequentially laminated on the one main surface (11a) of the substrate (11). The table below shows other conditions for forming these layers.

[0037]

[Table 2]

Reference numeral (17) is a block layer made of SiO ₂ laminated on the cap layer (16) by a sputtering method, and a stripe groove (18) having a width of 6 μm reaching the cap layer (16) is formed by etching. There is.

(19) is a p-type electrode consisting of an Au / Cr electrode in which a Cr film and an Au film are vacuum-deposited in this order on the exposed cap layer (16) and block layer (17), (2)
0) is a Cr film or S on the other main surface (11b) of the substrate (11).
Au / Sn / C in which an n film and an Au film are vacuum-deposited in this order.
It is an n-type electrode composed of an r electrode. These electrodes are 400
The heat treatment at ℃ makes ohmic contact with the cap layer (16) or the substrate (11).

A known intermediate layer of Ga _0.5 In _0.5 P may be provided between the p-type cladding layer (15) and the cap layer (16) for the purpose of suppressing an increase in operating voltage of the device.

Twenty-five devices of this example having the above structure were manufactured, and the oscillation threshold current when operating at room temperature by pulse driving was measured. The result is shown in FIG. In addition, as a comparative example, one main surface (11a) of the substrate (11) is
Twenty-five comparative devices having the same structure as the device of this example except that the buffer layer (12) was GaAs and the buffer layer (12) was inclined by 2 ° in the [110] direction from the (00) face and the same measurement was performed. The result is shown in FIG.

From FIGS. 3A and 3B, it can be seen that the device of this embodiment has less variation in the oscillation threshold current than the comparative device. Further, when the surface of each cap layer was observed after forming each semiconductor layer by the MOCVD method with the device of this example and the comparative device, it was found that 1000 to 10 with the comparative device.
The number of hillocks generated at 000 pieces / cm ² was 100 pieces / cm ² or less in the apparatus of this embodiment. From this, it is considered that the reason why the oscillation threshold current of the device of this embodiment has less variation is that the hillocks are reduced, that is, the crystallinity of the formed semiconductor layer is improved.

In the apparatus of this embodiment, the main surface (11a) of the substrate (11) is 5 ° in the [011] direction from the (100) surface.
Although an inclined surface was used, the inclination angle may be 5 ° or more, preferably 5 to 7 °. That is, if the inclination angle is less than 5 °, sufficient effect cannot be obtained for improving the crystallinity of the semiconductor layer to be formed, and if it exceeds 7 °, it takes time to form the inclined surface, which is not practical in manufacturing.

Further, the present invention is not limited to the oxide stripe type laser using SiO ₂ for the block layer, and it goes without saying that the present invention can be applied to semiconductor laser devices of various structures.

[0045]

According to the present invention, the underlayer GaAs
Due to the influence of the principal surface having a predetermined angle in the [011] direction from the (100) plane of the substrate, it is possible to suppress the generation of crystal defects in a layer formed in a later step, particularly the crystal defects in the initial growth process, As a result, the variation in the oscillation threshold current of the visible light semiconductor laser device is small, and the manufacturing yield is improved.

Further, since the main surface of the GaAs substrate is tilted from the (100) surface in the [011] direction by a predetermined angle, when the active layer is made of GaInP, the GaInP influences the main surface which is the underlying surface. Accordingly, the wavelength of the oscillation light generated from the active layer can be shortened.

Particularly, when the predetermined angle is 5 to 7 °, a preferable effect is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for manufacturing a semiconductor laser device according to the present invention.

FIG. 2 is a sectional view showing an embodiment of the device of the present invention.

FIG. 3 (a) and FIG. 3 (b) are characteristic diagrams in which the oscillation threshold currents of the example device of the present invention and the comparative device are measured, respectively.

FIG. 4 is a cross-sectional view showing a conventional device.

[Explanation of symbols]

 11 n-type GaAs substrate 11a One main surface 13 n-type clad layer 14 active layer 15 p-type clad layer

Claims (11)

[Claims] 1. A 5 ° angle from the (100) plane in the [011] direction.
A visible light semiconductor laser device comprising: a GaAs substrate having the inclined surface as a main surface; and an AlGaInP-based semiconductor layer including an active layer formed on the main surface. 2. A 5 ° angle from the (100) plane in the [011] direction.
A first conductivity type GaAs substrate having the inclined surface as a main surface, and a first conductivity type AlGaInP formed on the main surface
A clad layer, an active layer formed on the clad layer,
A visible light semiconductor laser device, comprising: a second conductivity type AlGaInP clad layer formed on the active layer. 3. A 5 ° angle from the (100) plane in the [011] direction.
The GaAs substrate having the inclined surface as the main surface, the semiconductor layer in which the generation of crystal defects in the initial growth process due to the inclination in the above direction is suppressed by being deposited on the main surface, and the semiconductor A visible light semiconductor laser device comprising an AlGaInP-based semiconductor layer including an active layer formed on the layer. 4. A 5 ° angle from the (100) plane in the [011] direction.
An AlGaI including a GaAs substrate having the inclined surface as a main surface, a semiconductor layer deposited on the main surface in which generation of crystal defects is suppressed, and an active layer formed on the semiconductor layer
A visible light semiconductor laser device comprising an nP-based semiconductor layer. 5. The visible light semiconductor laser device according to claim 1, wherein the active layer is made of GaInP. 6. A 5 ° angle from the (100) plane in the [011] direction.
A GaAs substrate having the inclined surface as a main surface, and an active layer made of GaInP that is formed on the main surface and generates oscillation light whose wavelength is shortened due to the inclination in the above direction Visible light semiconductor laser device. 7. A 5 ° angle from the (100) plane in the [011] direction.
A GaAs substrate having the inclined surface as the main surface, and an active layer made of GaInP formed on the main surface and whose photoluminescence emission energy increases due to the inclination in the above direction are characterized by being provided. Visible light semiconductor laser device. 8. A 5 ° angle from the (100) plane in the [011] direction.
An AlGaI layer including a GaAs substrate whose main surface is the inclined surface, and an active layer made of GaInP which is formed on the main surface and generates oscillation light whose wavelength is shortened due to the inclination in the above direction.
A visible light semiconductor laser device comprising an nP-based semiconductor layer. 9. A 5 ° angle from the (100) plane in the [011] direction.
A GaAs substrate having the inclined surface as a main surface, and an AlGaInP-based semiconductor layer including an active layer made of GaInP formed on the main surface and whose emission energy of photoluminescence increases due to the inclination in the above direction are provided. A visible light semiconductor laser device. 10. The inclined surface is a surface inclined by 5 ° to 7 °, 1, 2, 3, 4, 5,
The visible light semiconductor laser device according to 6, 7, 8 or 9. 11. The inclined surface is a polished surface, and the inclined surface is a polished surface.
9. The visible light semiconductor laser device according to 9 or 10.