JPH02210890A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent generation of surface level at a cleavage plane by irradiating the cleavage plane of a semiconductor laser with light having energy larger than the band gap of the semiconductor material, and then, after cleaning the cleavage plane with deionized water, coating with a Langmuir Blodgett film. CONSTITUTION:A plurality of stripe-shaped electrode metals 2 are welded to a predetermined part of a wafer, and this wafer is cleaved in the direction perpendicular to the stripe with a predetermined spacing to form a plurality of bar-shaped crystal members (chips) 4 with cleavage planes 3 which serve as mirrors for the laser. The cleavage planes 3 of the chips 4 are irradiated with light having energy larger than the band gap of the chip 4 in deionized water 8, and the cleavage planes 3 of the chips 4 are cleaned by the deionized water 8. Then, the cleavage planes 3 of the chips 4 are coated with a Langmuir Blodgett film. Thus, pollution of the cleavage plane 3 of the chips 4 can be prevented, and generation of surface level at the cleavage planes 3 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a semiconductor laser capable of obtaining high output.

[Conventional technology]

In recent years, in order to realize laser oscillation, it is generally necessary to provide two reflective surfaces parallel to each other and confine light between these two reflective surfaces to cause resonance.

In the case of a semiconductor laser, these two reflecting surfaces are formed by cleaving a crystal, and light generated within the semiconductor laser chip is reflected by the cleaved surfaces. In this way, the light resonates between the two cleavage planes, but since the reflectance of the cleavage planes is not 1, part of the light is emitted to the outside. This light emitted to the outside is used as the output light of the semiconductor laser.

By the way, as mentioned above, since there are two light reflecting surfaces, the output light can be extracted from the two surfaces. but,
In the normal use of semiconductor lasers, only the output light from one side is often used, so one side is coated with an end face coating that has a high reflectance, and the other side is coated with a coating that lowers the reflectance. The edge coating is applied to obtain stronger laser light from one side.In this case, the coating material is ^l!03.5i01.5.
Insulating films such as 13N4 and TiOx and Si films are used. Further, when forming a high anti-weight bearing end face, a metal such as Au may be used. Although the output characteristics of semiconductor lasers have been considerably improved by such end face coating technology, the output limit of semiconductor lasers is COD (Cataatrophic
This is determined by a phenomenon called optical damage.

This COD phenomenon is such that when the optical energy density in the semiconductor laser crystal exceeds a predetermined value, the laser end face is destroyed. The reason why such a COD phenomenon occurs is that surface states exist at the crystal end face. The surface level of this end face exists in the band gap. In particular, the surface level of GaAs, which is a typical material for semiconductor lasers, exists almost at the center of the band gap, which causes non-radiative recombination to occur when electrons and holes recombine.

In this non-radiative recombination process, heat is emitted instead of light.

The mechanism of this COD phenomenon is that light is first absorbed near the end face. Thereafter, electron-hole pairs are formed, and when these electron-hole pairs recombine, heat is generated and the temperature of the crystal increases near the end face. As a result, the band gap becomes smaller and the light absorption coefficient becomes higher. Therefore, many electron-hole pairs are generated.

When these electron-hole pairs recombine, they release heat and the temperature of the crystal further increases, a process that is repeated and COD
A phenomenon occurs.

Therefore, in order to prevent the COD phenomenon from occurring, it is necessary to lower the surface state density at the laser end face.

However, the conventional ``New and unified alodel model''
for 5chottky, barrler and
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J, Vac, Sci.

Technol, Vol. 16. N1515e
pt, 10ct, 197! IL No. 1422-1433
Page, tsuba, [! In the semiconductor laser of this type disclosed in ``Soccer et al.,'' co-authored by Spacer et al., no efforts were made to reduce the surface state density in the bandgap. Therefore, as a semiconductor laser having a relatively large output of several tens (1+W), there is a phase-locked semiconductor laser in which a large number of stripes are placed close to each other and synchronized with each other.

[Problem to be solved by the invention]

However, since the above-mentioned conventional phase-locked semiconductor laser has a high density of surface states in the band gap, the laser may be destroyed by light generated by instantaneous excessive current due to noise, static electricity, etc. There was a problem in that mode control and making the radiation beam unimodal became difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor laser which can easily control the mode and make the radiation beam unimodal, can provide high output, and is resistant to instantaneous overcurrent.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention includes a step of cleaving a wafer on which a plurality of electrode metals are formed in a stripe shape at predetermined intervals in a direction perpendicular to the stripes and forming a plurality of chips. , irradiating the cleavage plane of the chip with light having an energy greater than the bandgap of the chip in deionized water, and washing the cleavage plane of the chip with the deionized water; The method includes a step of coating a Langmuir-Blodgett film.

[For production]

In the present invention, the cleavage plane of the chip is irradiated with light having energy larger than the band gap of the chip in deionized water, and the cleavage plane of the chip is washed with deionized water, so that the cleavage that adhered when the chimp is opened is removed. Surface contaminants are removed. Thereafter, a Langmuir-Blodgett film is coated on the cleaved surface of the chip, thereby preventing contamination of the cleaved surface of the chip. As a result, generation of surface states at the arm opening plane is prevented, and the COD phenomenon is prevented.

〔Example〕

A first embodiment of the method of manufacturing a semiconductor laser of the present invention will be described below.
The figure shows the coating process diagram of the laser end face, and the figure 2 shows LB.
This will be explained by showing a cumulative deposition diagram of the film.

First, as shown in Figure 1 (al), LPE, MBE or M
A plurality of electrode metals 2 are welded in stripes to predetermined portions of a wafer 1 created by OCVD or the like.

Next, as shown in Part 1), the wafer 1 is cleaved at predetermined intervals in a direction perpendicular to the stripes,
A plurality of bar-shaped crystal bodies (chips) 4 are formed with cleavage planes 3 that serve as laser mirrors. At this time, since the cleavage operation is carried out in the atmosphere, the cleavage plane 3 is contaminated by oxygen in the atmosphere and forms surface levels.

After that, as shown in Fig. 1(e), there is a joint 5 in the middle.
A holder frame 7 is prepared in which one end of a bendable support 6 is fixed to the side. Then, the plurality of bar-shaped crystal bodies 4 are bundled. At that time, leave the cleavage plane 3 exposed.
After this, the bundle of bar-shaped crystal bodies 4 is supported by a holder frame 7. Next, the bundle of bar-shaped crystals 40 is placed together with the holder frame 7 into a container 9 containing deionized water 8 having a specific resistance of about 18 MΩ. At this time, the cleavage plane 6 is bent into an L-shape and placed with the other end protruding above the water surface. After cleaning the cleavage surface 3 by converting the attached contaminants into water-soluble substances by photochemical reaction and dissolving them in water,
On deionized water B, an LB membrane material 10 having a hydrophilic group and a hydrophobic group, which is a material for Langmier Air Project membrane (hereinafter referred to as LB membrane), is floated. At this time, the LB membrane material 10 floats with its hydrophilic groups facing the deionized water 8 surface.The LB membrane material 10 is 22 tricosenic acid: CHz = CH(CHt) t. -GOOR etc.

Next, as shown in FIG. 1(d), the cleavage plane 3 of the bar-shaped crystal body 4 held by the holder frame 7 is
As shown in FIGS. 2(al to (C1)), one layer of LBBi12 is deposited on the cleavage plane 3 every time the LBII material 10 is crossed.
Deposited. In this case, as a result of trial experiments, LBBi12
Since the interaction with cleavage plane 3 is extremely small, LBBi1
Even if 2 is attached, no surface level is generated in the band gap of the cleavage plane 3. Further, about 3 to 50 layers are deposited on the LBBi12 cleavage plane 3.

Thereafter, after depositing the LB film 11, a film having an appropriate reflectance and also serving as protection for the LBBi 12 is formed on the LB film 11 by sputtering or end face coating using a CVD method. Complete the laser.

Therefore, contamination of the cleavage plane 3 of the semiconductor laser is prevented, and the generation of surface levels in the band gap at the cleavage plane 3 is prevented, thereby preventing COD destruction and making it possible to increase the output of the laser. Furthermore, by preventing the generation of surface levels in the band gap, it is possible to prevent the relay laser from being destroyed, which is resistant to light generated by instantaneous excessive current due to noise, static electricity, or the like.

〔Effect of the invention〕

As explained above, according to the present invention, the cleavage plane of a semiconductor laser is irradiated with light having energy larger than the bandgap of the semiconductor material, and after the cleavage plane of the laser is cleaned with deionized water, Since the air projector film is coated, contamination of the cleavage plane can be prevented, and as a result, generation of surface states on the cleavage plane can be prevented.

Therefore, destruction of the cleavage plane due to COD can be prevented, and a laser with high output that is easy to control modes and make single peaks can be obtained.It is also resistant to instantaneous overcurrent caused by noise, static electricity, etc., and the destruction of the laser can be prevented. can.

[Brief explanation of the drawing]

1 and 2 show an embodiment according to the present invention, in which FIG. 1 is a coating process diagram of a laser end face, and FIG. 2 is a cumulative deposition diagram of an LB film. 1... Wafer, 2... Electrode metal, 3... Cleavage plane,
4...Bar-shaped crystal, 5...Joint, 6...
Rod, 7...Holder frame, 8...Ionized water, 9...
- Container, 10... LB film material, 11... LB film. Coating process diagram for laser end face Fig. 1 Coating process diagram for laser end face Fig. 1

Claims (1)

[Claims] A wafer on which a plurality of electrode metals are formed in a stripe shape,
A process of forming a plurality of chips by cleaving at predetermined intervals in a direction perpendicular to the stripes, and irradiating the cleavage plane of the chip with light having an energy higher than the band gap of the chip in deionized water. A method for manufacturing a semiconductor laser, comprising the steps of: cleaning the cleavage plane of the chip with the deionized water; and then coating the cleavage plane of the chip with a Langmuir-Blodgett film.