JPH07283484A - Manufacture of semiconductor laser element - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a semiconductor laser element, which can form a semiconductor layer, whose band gap is enlarged, on a resonator surface at a high yield. CONSTITUTION:In a method of manufacturing a semiconductor laser element of a structure/wherein a semiconductor laser 11 having a band gap larger than that of an active layer 5 is laminated on a resonator surface on the active layer 5, a process/in which a dielectric layer 10 is formed on the lamination surface of an epitaxial semiconductor wafer laminated with the layer 5, then, the wafer is cleaved to form the resonator surface, then, the layer 11 having the band gap larger than that of the layer 5 is laminated on the resonator surface, then, the layer 10 is removed by etching is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high power driven semiconductor laser device.

[0002]

2. Description of the Related Art In recent years, as the applications of GaAs semiconductor laser devices have expanded, the demand for high output driving has increased. By the way, as the light output of the semiconductor laser device is increased, optical damage that is instantaneously deteriorated and end face corrosion that occurs when the semiconductor laser device is operated for a long time are observed.
It is considered that this is because the cycle of the phenomenon of light absorption → increase in surface recombination current → increase in end face temperature is repeated. In this case, the deterioration becomes remarkable as the light density at the end face increases. In some cases, a phenomenon is observed in which instantaneous deterioration is induced and oscillation is suddenly stopped. Therefore, in order to suppress such a phenomenon at the laser end face of the semiconductor laser element, a structure (window structure) that does not cause light absorption at the end face is provided. Specifically, there is a method of providing a portion for enlarging the band gap of the active layer on the end face to prevent light absorption and prevent optical damage. For a semiconductor laser device having such a structure, after a laser resonator manufacturing process such as mesa formation is completed, a semiconductor layer having a band gap larger than that of the active layer is stacked on the resonator surface by MOCVD or the like. Attempts have been made to widen the gap.

Conventionally, the step of laminating a semiconductor layer having a bandgap larger than that of the active layer on the cavity facet of a semiconductor laser device has been performed as follows. That is, 1) As shown in FIG. 3A, an epitaxial layer 32 including an active layer is laminated on a semiconductor substrate 31, and a reflection end face 33 is formed by etching. 2) Next, as shown in FIG. 3B, a semiconductor layer 34 having a band gap larger than that of the active layer is selectively grown on the end face 33. 3) Next, an electrode is formed on the epitaxial layer 32,
Cleave at cleavage position A. 4) Finally, a low reflection film is formed on the end face 33.

[0004]

However, the conventional process of laminating a semiconductor layer having a bandgap larger than that of the active layer on the cavity face has the following problems. That is, since the reflective end face 33 is formed by etching, the reflective end face 3 is perpendicular to the epitaxial layer 32 and is excellent.
3 was difficult to form, and there was a problem that the manufacturing yield was reduced.

[0005]

The present invention provides a method of manufacturing a semiconductor laser device which solves the above problems.
In a method of manufacturing a semiconductor laser device in which a semiconductor layer having a bandgap larger than that of an active layer is stacked on a cavity surface of an active layer, a first dielectric layer is formed on a stacked surface of an epitaxial semiconductor wafer on which an active layer is stacked, and Forming a second dielectric layer that can be removed independently of the first dielectric layer, then cleaving the wafer to form a resonator surface, and then forming a bandgap on the resonator surface. Is a first invention having a step of laminating a semiconductor layer larger than the active layer and then removing the second dielectric layer independently of the first dielectric layer.

Further, a semiconductor layer including an active layer is epitaxially grown on the substrate, a semiconductor layer having a band gap larger than that of the active layer and a reflective film are laminated on the resonator surface, and electrodes are formed on the epitaxial growth surface and the back surface of the substrate. In a method for manufacturing a semiconductor laser device, an epitaxial semiconductor wafer in which a semiconductor layer including an active layer is epitaxially grown on a substrate is cleaved to form a resonator surface on a low reflection side,
Then, a semiconductor layer having a bandgap larger than that of an active layer is laminated on the resonator surface, a reflection film is laminated on the resonator surface, and then the reflection film is used as a mask except on the resonator surface. A second invention has a step of etching and removing a semiconductor layer having a bandgap larger than that of the active layer.

[0007]

As in the first invention, on the cleaved resonator surface,
When a semiconductor layer having a band gap larger than that of the active layer is stacked, the semiconductor layer grows not only on the cavity plane but also on the dielectric layer. At this time, the semiconductor layer on the resonator surface is chemically bonded to the semiconductor forming the resonator surface, but the semiconductor layer on the dielectric layer is simply in a polycrystalline state on the dielectric layer. Only deposited, not chemically bonded to the dielectric layer. Therefore, if the dielectric layer is to be removed by etching in the next step, the etchant can easily pass through the semiconductor layer deposited on the dielectric layer to reach the dielectric layer and remove the dielectric layer. As a result, the semiconductor layer on the dielectric layer is also removed, and a semiconductor layer having a wide bandgap can be formed only on the resonator surface with high yield.

When a semiconductor layer having a bandgap larger than that of the active layer is stacked on the resonator surface as in the second invention, this semiconductor layer is also stacked on the epitaxial growth surface. On the other hand, the reflective film that can be laminated at a low temperature can be formed only on the resonator surface by masking the epitaxial growth surface. Therefore, by using this reflective film as a mask, it is possible to etch and remove a semiconductor layer stacked on a portion other than the resonator surface and having a bandgap larger than that of the active layer. In this way, a semiconductor layer having a bandgap larger than that of the active layer can be formed only on the resonator surface with high yield.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. (Embodiment 1) FIG. 1 is a process explanatory view of an embodiment of a method for manufacturing a semiconductor laser device according to the present invention. Figure 1 (a)
(C) and (f) are transverse sectional views, and (d) and (e) are longitudinal sectional views at the ridge head. The steps of this example are as follows. That is, 1) First, on an n-GaAs substrate 1 having a plane orientation (100), an n-GaAs buffer layer 2 having a thickness of 0.5 μm, an n-AlGaAs lower cladding layer 3 having a thickness of 2.0 μm, and a thickness of 5 are formed.
0 nm GaAs lower optical confinement layer 4, 9 nm thick In
Active layer 5 consisting of GaAs strained quantum well layer, thickness 50n
optical confinement layer 6 on GaAs having a thickness of 2.0 μm and p-
AlGaAs upper cladding layer 7, 0.5 μm thick p-G
The aAs cap layer 8 is sequentially laminated. 2) Next, the cap layer 8 and the upper cladding layer 7 are etched to form a ridge mesa (FIG. 1A). 3) Next, a SiO _x layer 9 is laminated as a first dielectric layer for confining the injection current, and a window is formed in the ridge head portion by a photolithography technique for electrode contact (FIG. 1B). 4) Next, the AlO _x layer 10 is formed on the SiO _x layer 9 (FIG. 1C). 5) The epitaxial wafer thus formed is polished to a thickness of 110 μm and then cleaved (110).
The end face is exposed, and the InO having a band gap larger than that of the active layer 5 is formed on the end face by using the AlO _x layer 10 as a selective growth mask.
The GaP layer 11 is grown (FIG. 1 (d)). At this time, I
The nGaP layer 11 is also laminated on the AlO _x layer 10. Here, the InGaP layer 11a laminated on the end face is chemically bonded to the end face of the substrate 1 and the epitaxial layer grown thereon. On the other hand, I deposited on the AlO _x layer 10
The nGaP layer 11b is not chemically bonded to the AlO _x layer 10 and is simply deposited on the AlO _x layer 10 in a polycrystalline form. 6) Next, the AlO _x layer 10 is removed with a strong alkaline solution to remove only the InGaP layer 11b of the InGaP layer 11 stacked on the AlO _x layer 10, and SiO _x.
Expose the layer 9 and the cap layer 8 of its window (FIG. 1).
(E)). In this step, since the InGaP layer 11b is not bonded chemically AlO _x layer 10 in polycrystalline form, strong alkaline solution through the InGaP layer 11b, easily reached AlO _x layer 10, AlO _x layer 10 Can be dissolved. At this time, the SiO _x layer 9 and the cap layer 8 are not attacked by the alkaline liquid. 7) Next, on the epitaxial surface side and the substrate 1 side,
Ti / Pt / Au electrode 12, AuGeNi / A, respectively
The u electrode 13 was vapor-deposited to manufacture a ridge waveguide semiconductor laser device having a width of 3 μm and a cavity length of 1 mm (FIG. 1 (f)).
In addition, on the end face, a dielectric with a reflectance of 5% on the low reflection side,
The high reflection side was coated with a dielectric having a reflectance of 95%.

In this embodiment, the InGaP layer 1 is formed on the end face.
The yield reduction due to the step of growing No. 1 could be suppressed to 10%. In addition, the element of the above embodiment,
A constant light output operation test was performed at 200 mW. As a result, assuming that a failure occurred when the drive current increased by 50%, the failure rate was 5000 FIT at room temperature. However, failure rate F
IT is FIT = number of failures / (operating time × operating number) × 10
^It is defined as ⁹ . In this example, the total yield of device fabrication including the edge growth process was about 70%. On the other hand, the yield without edge growth was 80%, and the decrease in yield due to the edge growth process could be suppressed to about 10%. From this, according to the present invention,
High-output and highly reliable semiconductor laser devices can be manufactured with high yield.

(Embodiment 2) FIGS. 2A to 2C are sectional explanatory views of respective steps of another embodiment of the method for manufacturing a semiconductor laser device according to the present invention. 2A to 2C and 2F are cross-sectional views,
(D) And (e) is a longitudinal cross-sectional view of the ridge head. The steps of this example are as follows. That is, 1) First, on an n-GaAs substrate 1 having a plane orientation (100), an n-GaAs buffer layer 2 having a thickness of 0.5 μm, an n-AlGaAs lower cladding layer 3 having a thickness of 2.0 μm, and a thickness of 5 are formed.
0 nm GaAs lower optical confinement layer 4, 9 nm thick In
Active layer 5 consisting of GaAs strained quantum well layer, thickness 50n
optical confinement layer 6 on GaAs having a thickness of 2.0 μm and p-
AlGaAs upper cladding layer 7, 0.5 μm thick p-G
The aAs cap layer 8 is sequentially epitaxially grown. 2) Next, the cap layer 8 and the upper clad layer 7 are etched to form a ridge mesa (FIG. 2A). 3) Then Si as a dielectric layer for injection current confinement
The O _x layer 9 is laminated, and a window is formed in the ridge head by photolithography technique for electrode contact (FIG. 2).
(B)). 4) After polishing the epitaxial wafer thus formed to a thickness of 110 μm, it is cleaved with a width twice the cavity length to expose the (110) end face, and the end face is exposed to a band more than the active layer 5. The InGaP layer 20 having a large gap is grown. At this time, I was formed on the SiO _x layer 9 on the epitaxial growth surface and on the cap layer 8 on the ridge head.
A polycrystalline semiconductor layer 20a made of n, Ga and P is laminated (FIG. 2C). The cleavage planes on both sides are low reflection planes, and the planes cleaved to half the cavity length are high reflection planes. 5) Next, the dielectric reflection film 21 made of Al ₂ O ₃ having a reflectance of 5% is laminated only on the InGaP layer 20 on the end face (FIG. 2D). 6) Next, using the reflective film 21 on the end face and the SiO _x layer 9 on the epitaxial growth surface as an etching mask, a large amount of In, Ga and P formed on the SiO _x layer 9 and the cap layer 8 forming the ridge head is formed. Crystal semiconductor layer 20
a is removed by etching (FIG. 2E). For this etching, an etchant having a large selection ratio of GaAs and InGaP is used. 7) Next, cleavage is performed to a width of the cavity length, and Ti / Pt / Au electrode 12 and AuGeNi / Au electrode 13 are vapor-deposited on the epitaxial surface side and the substrate 1 side, respectively, and Al ₂
A multilayer film made of a SiN _x film and an amorphous Si film having a reflectance of 95% is formed on the resonator surface opposite to the end surface coated with the dielectric reflection film made of O ₃ (FIG. 2 (f)).

The completed ridge waveguide type semiconductor laser device has a current injection width of 3 μm and a cavity length of 1 mm. When the device of this example was subjected to a constant light output operation test under the same conditions as in the above example, the same favorable result as in the above example was obtained. Further, the manufacturing yield was also improved as in the above-mentioned embodiment. It is needless to say that the present invention is not limited to the ridge waveguide type semiconductor laser device of the above embodiment, but can be applied to a semiconductor laser device using other means for current constriction.

[0013]

As described above, according to the present invention, in a method of manufacturing a semiconductor laser device in which a semiconductor layer having a band gap larger than that of the active layer is laminated on the cavity surface of the active layer, an epitaxial layer in which the active layer is laminated is used. Forming a first dielectric layer and a second dielectric layer that can be removed independently of the first dielectric layer on a laminated surface of a semiconductor wafer;
Then, the wafer is cleaved to form a resonator surface, a semiconductor layer having a bandgap larger than that of an active layer is stacked on the resonator surface, and then the second dielectric layer is formed on the first dielectric layer. An excellent effect that a bandgap widening semiconductor layer can be formed on the resonator surface with a high yield and a high-power semiconductor laser device can be manufactured because it has a step of removing the dielectric layer independently. There is. Also,
An epitaxial semiconductor wafer in which a semiconductor layer including an active layer is epitaxially grown on a substrate is cleaved to form a resonator surface on the low reflection side, and then a semiconductor layer having a band gap larger than that of the active layer is formed on the resonator surface. Then, a reflective film is laminated on the resonator surface, and then the semiconductor layer having a band gap larger than that of the active layer is removed by etching using the reflective film as a mask, which is laminated except on the resonator surface. The same excellent effect can be obtained by the method including the step of

[Brief description of drawings]

1A to 1F are process explanatory views of an embodiment of a method for manufacturing a semiconductor laser device according to the present invention.

2A to 2F are process explanatory views of another embodiment of the method for manufacturing a semiconductor laser device according to the present invention.

3A and 3B are process explanatory views of a conventional method for manufacturing a semiconductor laser device.

[Explanation of symbols]

1 substrate 2 buffer layer 3, 7 clad layer 4, 6 optical confinement layer 5 active layer 8 cap layer 9 SiO _x layer 10 AlO _x layer 11, 11a, 11b InGaP layer 12, 13 electrode 20 InGaP layer 20a polycrystalline semiconductor layer 21 Dielectric reflective film

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor laser device, wherein a semiconductor layer having a bandgap larger than that of an active layer is laminated on a cavity surface of the active layer, wherein a first dielectric is formed on a laminated surface of an epitaxial semiconductor wafer on which the active layer is laminated. A body layer and a second dielectric layer that can be removed independently of the first dielectric layer, and then cleaves the wafer to form a resonator surface, and then the resonator. A semiconductor laser device comprising a step of laminating a semiconductor layer having a bandgap larger than that of an active layer on the surface, and then removing the second dielectric layer independently of the first dielectric layer. Manufacturing method. 2. A semiconductor layer including an active layer is epitaxially grown on a substrate, a semiconductor layer having a band gap larger than that of the active layer and a reflective film are laminated on a cavity surface, and electrodes are formed on the epitaxial growth surface and the back surface of the substrate. In a method for manufacturing a semiconductor laser device, an epitaxial semiconductor wafer in which a semiconductor layer including an active layer is epitaxially grown on a substrate is cleaved to form a resonator surface on the low reflection side, and then a band gap is formed on the resonator surface. A semiconductor layer larger than the active layer is stacked, then a reflective film is stacked on the resonator surface, and then the bandgap stacked except on the resonator surface with the reflective film as a mask is larger than that of the active layer. A method of manufacturing a semiconductor laser device, comprising the step of etching and removing a large semiconductor layer.