JPS6120384A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To contrive the end-surface deterioration of a laser resonator in the state of high output, by a method wherein stepwise differences larger than the film thickness of an active layer are formed at both ends of the active layer, thus making the composition of a layer located at the laser resonator end- surface larger than that of said active layer. CONSTITUTION:The stepwise differences 11' levelled down from a substrate 10 are formed at both its ends in the direction cleavage: the center part is of the form of a rise in projection. Each of layers laminated on the surface of this substate is of the same form as that of said substrate 10. Since the composition of the active layer 21 is AlYGa1-YAs and that of the upper clad layer is AlXGa1-Y As, use of the above-mentioned semiconductor laser 1 makes a clad layer 22 located at both end-surfaces of the active layer 21 in the presence of the stepwise differences 11' and therefore yields a substantial aluminum composition of X. Besides, the composition ratio is: X>Y, therefore, the band gap of the laser resonator end-surface comes to enlarge. In other words, the light absorption in this part decreases, thereby inhibiting the heat developing in the end surface in the state of high output.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a GaAlAs semiconductor laser and a method for manufacturing the same.

(b) Prior Art Recently, as GaAlAs-based semiconductor lasers have been made to have higher output, they tend to have the problem of destroying the laser resonator end face due to their own power. The following methods are being considered as countermeasures.

■ A method of making the cleavage plane on the optical output side of a semiconductor laser non-reflective and making the cleavage plane on the opposite side highly reflective.

■ A method of reducing the edge light density by making the active layer extremely thin so that light seeps out of the active layer.

The two methods described above are certainly effective in preventing the end face of the laser resonator from being destroyed at high output. However, this causes the following problems.

In method (2), the cleavage plane is processed after the laser wafer is cleaved, which makes it very difficult to handle.

Therefore, a problem arises in that the processing technology becomes extremely sophisticated.

On the other hand, in method (■), by making the active layer thinner,
The optical characteristics inevitably change. moreover,
The problem arises that the manufacturing technology is relatively difficult.

(c) Objective The first object of the invention is to provide a semiconductor laser that can alleviate end face deterioration of a laser resonator at high output.

The second invention aims to provide a method for manufacturing a semiconductor laser which eliminates the troublesome handling during the manufacturing process and which requires relatively simple processing techniques.

(D) Structure The semiconductor laser according to the first invention has step portions that are larger than the film thickness of the active layer at both ends of the active layer, so that the composition of the layer located at the end face of the laser resonator is adjusted to the active layer. It is characterized by being larger than the composition of the layer.

A method for manufacturing a semiconductor laser according to the second invention includes forming a groove along the direction in which a semiconductor substrate is to be cleaved, and forming a lower cladding layer, an active layer, and an upper cladding layer on the surface of the substrate. The active layer is characterized in that step portions are formed at both ends of the active layer by stacking the layers and separating the devices by cleaving them along the grooves.

(e) Embodiment 2. Optical location FIG. 1 is a perspective view showing an embodiment of the semiconductor laser according to the first invention.

In the figure, 1 is a semiconductor laser, 10 is an N-type GaA
s substrate, 20 is a lower cladding layer made of N-type Al x Gap-xAs, 21 is an active layer made of ^ly Ga1-yAs, 22 is an upper cladding layer made of P-type Al Type AI) (Gal
-× to cap layer made of S, 24 is an insulating film with stripe-shaped windows, 30 is a P-type stripe electrode, 31
indicate N-type electrodes, respectively.

Specifically, stepped portions 11' are formed at both ends of the substrate 10 in the direction of cleavage, and the stepped portions 11' are protruded in a convex shape at the center. Furthermore, each layer laminated on the surface of this substrate also has the same shape as the substrate 10. Note that the difference between the stepped portion 11'' and the raised portion is smaller than the film thickness of the upper cladding layer 22, and the active W1
The film thickness is made larger than that of No. 21.

According to the semiconductor laser 1 described above, the aluminum composition on both end faces of the active layer 21 is substantially x due to the stepped portion 11''.
>Y, the bandgap of the laser resonator end face is widened.

That is, by reducing light absorption in this portion, it is possible to suppress heat generated at the end face of the laser resonator during high output.

Figure 2 shows an explanatory view of one embodiment of the method for manufacturing the semiconductor laser shown in Figure 1, and shows a cross-section from Figure 1 to Figure 1. Note that the same parts as in FIG. 1 are indicated by the same reference numerals.

tdl The surface of the semiconductor substrate 10 other than the portion to be cleaved is covered with a photoresist 40. Using this photoresist 40 as a mask, plasma etching is performed to an appropriate depth to form a concave groove 11.

(b) On the surface of the substrate 10 from which the photoresist 40 has been removed, a lower crat layer 20, an active layer 21, an upper crat layer 22, and a camp layer 23 are successively grown using, for example, an MBIE apparatus.

[C1 An insulating film 2 is formed on the surface of the cap layer 23 grown above.
4.

tdl The surface of the substrate other than the portion where the contact hole of the P-type electrode 30 is to be opened is covered with photoresist (not shown). Using this photoresist as a mask, the insulating film 24 is selectively etched (not shown). Thereafter, each electrode is formed in the same manner as in a normal semiconductor laser manufacturing method.

(e) At the substrate end of the groove 11 formed in the substrate, a scratch is made in the same direction as the groove 11 using, for example, a diamond cutter. And this (1k (cleaved cotton)
By applying an external force to cleave in the direction along the groove portion 11, a step portion 1B (the bottom is a step) is formed in the vicinity of the cleavage plane of the substrate 10 and each layer laminated on this surface. . Furthermore, the separated parts are separated into individual elements to form a semiconductor laser.

The width of the groove 11 in the second embodiment of the invention described above is preferably such that the cleaved cotton can fit in the lower part of the groove 11.

Furthermore, in the embodiments of the first and second inventions described above,
The step portions 11° formed at both ends of the active FFI 21 are not limited to steps that go down below the active layer 21, but may be steps that go up above the active layer 21. In this case, the grooves 11 of the substrate 10 on the cleavage plane are manufactured to be convex raised portions, and the raised portions are manufactured to be concave grooved portions.

(f) Effect The first invention forms step portions larger than the film thickness of the active layer at both ends of the active layer, and makes the composition ratio of the laser resonator end face larger than the composition ratio of the active layer. Since the hand gear knob at this end portion widens, the light absorption rate decreases significantly. Therefore, heat generated in this portion can be suppressed, and as a result, end face deterioration during high output can be alleviated.

According to the second aspect of the invention, the step portion of the laser resonator end face is formed on the substrate before it is separated, so that there is no trouble or difficulty in manufacturing. Further, the semiconductor laser described above can be formed using conventional technical processes without requiring any special technology.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the semiconductor laser according to the first invention, and FIG. 2 is an explanatory diagram of an embodiment of the method for manufacturing the semiconductor laser shown in FIG. DESCRIPTION OF SYMBOLS 1... Semiconductor laser, 10... Semiconductor substrate, L... Groove portion, II''... Step portion, 20... Lower cladding layer, 21... Active layer, 22... Upper cladding layer .Patent Issue 1 Uto ROHM Co., Ltd. Agent Patent Attorney Takaharu Onishi tJ1 Diagram

Claims (2)

[Claims] (1) A semiconductor laser having a double heterojunction structure includes a lower cladding layer made of Al_XGa_1_-_XAs, an active layer made of Al_YGa_1_-_YAs, and an upper cladding layer made of Al_XGa_1_-_xAs, and the composition ratio is set to >Y, and step portions larger than the thickness of the active layer are formed at both ends of the active layer. (2) A method for manufacturing a semiconductor laser having a double heterojunction structure, including the step of forming a groove along the direction in which the semiconductor substrate is to be cleaved, and the step of forming an Al_XGa_1 on the surface of the substrate in which the groove is formed.
_-_ lower cladding layer made of XAs and Al_YGa
_1_-_active layer made of YAs and Al_XGa_1
By stacking an upper cladding layer made of ____XAs and separating each element by cleaving along the groove, a step larger than the thickness of the active layer is formed at both ends of the active layer. 1. A method of manufacturing a semiconductor laser, comprising the step of forming a portion.