JPH09162501A - Method and jig for passivating semiconductor laser end - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-power semiconductor laser of high reliability by reducing surface level and preventing reduction in COD level. SOLUTION: A semiconductor laser being manufactured being manufactured of which is not formed is cleaved in an atmosphere containing no oxygen. An end formed in this step is treated by a treatment liquid which is placed in the atmosphere and acts to prevent generation of surface level of the semiconductor laser. The treated end is covered with an end protecting material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a passivation method for an end face of a high power semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, various semiconductor lasers having a semiconductor layer laminated on a GaAs substrate have been proposed. Such a semiconductor laser has a GaAs / AlGaAs (quantum well) or InGaP active layer of 0.6 to 0.8 μm.
It generates m-band laser light and is used for optical information recording and optical information recording / reproduction. In recent years, InGaAs / GaAs
A laser having a wavelength band of 0.8 to 1 μm using a strained quantum well layer as an active layer is formed on a GaAs substrate and used as an excitation light source for a fiber amplifier. These lasers are required to operate at high output, but there is a problem in that they have a short life during high output operation.

Several studies have been conducted so far on the cause of deterioration of the semiconductor laser. These are COD (Catastrophic Optical Dam) destruction of the end face of the resonator.
age), surface alteration, growth of crystal dislocation defects, and other damages of ohmic electrodes and generation of point defects. In particular, in a semiconductor laser having a semiconductor layer laminated on a GaAs substrate, it has been pointed out that the COD of the cavity end face is an important cause of deterioration of the life of the laser in high-power operation. This C
The OD is due to the fact that the vicinity of the cavity end face of the semiconductor laser is an absorption region for laser light. That is, this type of COD starts with a decrease in the bandgap caused by a temperature rise due to non-radiative recombination via surface levels existing on the surface of the semiconductor crystal. This bandgap reduction is accompanied by feedback that the temperature further rises. As a result, melting of the end face is induced, the light output is reduced, and irreversible destruction occurs. The antireflection film and the high reflection film provided on the end surface of the high power semiconductor laser have an effect of suppressing this COD. That is, the antireflection film and the high reflection film function as an end face protective material. However, even if the end surface is covered with such a protective material, it is not possible to completely prevent COD, and in particular, it frequently occurs at the end surface on the light emitting side where the antireflection film is formed.

It has been pointed out that it is important to remove the surface level formed by the reaction with oxygen at the cavity facets in order to increase the critical light output of COD. Recently, (N
It has been reported that the treatment of H ₄ ) ₂ S _x , P ₂ S ₅ (NH ₄ ) ₂ S and Na ₂ S aqueous solutions has an effect of improving the surface characteristics of GaAs. This sulfide treatment removes natural oxides on the surface, and the bonds of surface atoms are covered with sulfur atoms,
It is possible to suppress the subsequent oxidation process and increase in the surface level.

By the way, most of the examinations of the device application of the sulfide treatment relate to electronic devices,
There are few things related to optical devices. Some of them are shown below. The invention of Peter Leo Poufmann et al., "Method of Passivating Etching Mirror Facet of Semiconductor Laser" (JP-A-6-342961). In the present invention, the damage layer is removed from the laser end face formed by etching by wet etching, and (NH ₄ )
By applying ₂ S _x and Na ₂ S treatments, a laser comparable to the conventional laser having a cleaved end face can be obtained. The invention “Semiconductor Light-Emitting Device” by Toshiaki Tanaka et al. (JP-A-6-268327). According to the present invention, the semiconductor laser is cleaved into bars and subjected to (NH ₄ ) ₂ S _x treatment, and the stress introduced by the end face protective material formed thereafter is used to increase the band gap near the end faces and suppress light absorption. That is. In the present invention, it is not clear that the effects of sulfide treatment and stress introduction are separated, and the degree of effect of sulfide treatment is unknown. The invention of Hiroyuki Ota et al., "Method for manufacturing semiconductor laser" (Japanese Patent Laid-Open No. 7-66485). In the present invention, the sulfide treatment is promoted by applying an electric field between the laser and the other electrode during the sulfide treatment. The conventional passivation method of the cleaved end face of the semiconductor laser by the sulfide treatment is performed only by the method of subjecting the laser bar formed by cleavage in air to the sulfide treatment.

[0006]

The above-mentioned conventional passivation method of the cleaved end face of the semiconductor laser by the sulfide treatment includes a step of cleaving in the air to form a laser bar, so that Al such as AlGaAs is a constituent element. In a semiconductor laser including a layer, an oxide formed by oxidation immediately after cleavage is stable, and has a drawback that it remains without being completely removed by a subsequent sulfide treatment. The present invention is intended to provide a novel method for passivating a cleaved end face of a semiconductor laser, which does not have such drawbacks.

[0007]

A first means of the present invention is as follows.
Before forming the end face protection material, the end face treatment is performed by cleaving in an atmosphere containing no oxygen and using the end face treating liquid placed in the same atmosphere. The second means of the end face of the semiconductor laser according to the present invention is to cleave in the end face processing liquid. A third means of the present invention is to fix the semiconductor laser to a jig when cleaving the semiconductor laser in the end surface treatment liquid. The fourth means of the present invention is to form the end face protective material by installing the laser bar on the device for forming the end face protective material with the laser bar fixed to the jig even after the cleavage.

According to the first and second means of the present invention, unlike the conventional passivation method for the end face of a semiconductor laser, a step of cleaving in air is not included, and the process is performed in an oxygen-free atmosphere or in a facet treatment liquid. Since the cleavage is performed, the sulfide treatment can be performed before the oxidation, and thus the treatment without the residual oxide can be performed. Therefore, since the surface level is reduced and the COD level is suppressed from being lowered, a highly reliable high power semiconductor laser can be realized.

As in the second means, when a sharp knife or the like is brought into contact with the side surface of the semiconductor laser wafer when cleaving in the sulfide solution, the semiconductor laser wafer moves due to a decrease in frictional force in the solution. It is difficult to cleave at the position. Furthermore, it is difficult to handle the laser bar in the sulfide solution, and handling with tweezers or the like easily damages the semiconductor laser.

On the other hand, according to the third means of the present invention,
Cleavage of the semiconductor laser in the end surface treatment liquid can be performed in a state of being fixed to a jig having a certain weight (third means), so that the semiconductor laser wafer does not move in the solution and is kept at a predetermined position. Cleavage is possible. Further, even after the cleavage, the laser bar is fixed to the jig, and it is possible to install the end face protective material as it is in the apparatus for forming the end face protective material (fourth means), and then in the sulfide solution. It is possible to provide a passivation method for an end face of a semiconductor laser, which is free from the drawback of being damaged by handling.

In other words, according to the present invention, the first step of cleaving the semiconductor laser in the process of manufacture, in which at least one end face is not formed, in an atmosphere not containing oxygen, and the step of placing the semiconductor laser in the atmosphere, A second step of treating the end face formed in the first step with a treatment liquid having an action of suppressing the generation of the surface level of the semiconductor laser, and an end face of the end face treated in the second step. A feature of the invention is a method of passivating an end face of a semiconductor laser, which includes a third step of covering with a protective material.

Further, according to the present invention, a pair of fixing plates 17 are formed, in which at least one end face is not formed, and which forms a recess for dropping the semiconductor laser in the process of manufacture, and the fixing plate 17.
Another feature of the invention is a jig including a pair of crimping plates 18 for crimping the semiconductor laser and a positioning base 16 having a groove for separately accommodating the pair of fixing plates 17 at an interval required for cleavage. To do.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention comprises a first step of cleaving a semiconductor laser in the process of manufacture, in which at least one end face is not formed, in an atmosphere containing no oxygen, and the step of placing the semiconductor laser in the atmosphere. A second step of treating the end face formed in the first step with a treatment liquid having an action of suppressing the generation of the surface level of the semiconductor laser, and an end face of the end face treated in the second step. A feature of the invention is a method of passivating an end face of a semiconductor laser, which includes a third step of covering with a protective material.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 FIG. 1 is a diagram showing a cross section of a laser according to Example 1 of the present invention. In the figure, 1 is an n ⁺ -GaAs substrate, 2 is n
-GaAs buffer layer, 3 is n-AlGaAs cladding layer, 4 and 8 are AlGaAs guide layers, 5 and 7 are AlGaAs SCH layers, 6 is InGaAs strained quantum well active layer, 9 is p-AlGaAs cladding layer, 10 is p ⁺ -
GaAs contact layer, 11 is insulating layer, 12 is p electrode,
13 is an n electrode.

In order to realize this structure, an epitaxial crystal growth apparatus (MOCVD method: metal organic chemical vapor deposition apparatus or MBE method: molecular beam epitaxy method) is used to form an n ⁺ -GaAs substrate 1 as shown in FIG. The epilayers 2 to 10 are grown. In the MOVPE method, trimethylindium (TMI), triethylgallium (TEG), trimethylaluminum (TMA), arsine (AsH ₃ ) are used as raw materials for semiconductor thin film growth, and hydrogen selenide (H ₂ Se) and p are used as n-type dopants. Diethyl zinc (DEZn) was used as the type dopant. The epitaxial growth temperature is about 700 ° C., the growth pressure is about 0.1 atm,
The carrier gas is hydrogen. In the MBE method, metallic gallium (Ga), indium (In), aluminum (Al), and arsenic (As solid) are used as raw materials, silicon (Si) is used as an n-type dopant, and zinc (Z) is used as a p-type dopant.
n) was used. The epitaxial growth temperature is about 650
The growth pressure is about 10 ^-5 Torr.

After the growth, the contact layer 10 and the cladding layer 9 are processed to form a ridge having a width of about 1.5 to 3 μm. For that purpose, resist patterning is performed by photolithography, and using this as a mask, 10 or 9 layers are etched by wet or dry etching. The depth is determined in consideration of the transverse mode, and the guide layer 8 may be etched in some cases. After forming the ridge, the insulating film 1 is formed by sputtering or the like.
1 (SiO ₂ etc.) is formed on the entire surface, and SiO ₂ in the current injection region above the ridge is etched off, and then Cr / Au is formed.
Alternatively, the p-electrode 12 made of Ti / Pt / Au or the like is formed.
Then, the back surface is polished to a thickness of 100 μm, and AuGeNi
And n-electrodes 13 are formed. After that, ohmic sintering is performed to form an electrode portion. The laser wafer thus formed is cleaved in the direction perpendicular to the stripe direction to obtain a width of 1.8 m.
The wafer 14 is divided into wafers 14 each having a length of m and a length of 10 mm. The width of this wafer is twice the cavity length of the final laser.
Further, a scribe 15 having a size of about 1 mm is placed in the center of the wafer 14 in the width direction.

This wafer is fixed to a cleavage jig. This jig has a guide groove in which the position of the second lower jig 17 (fixing plate) is determined by the first jig 16 (positioning table), and the second lower jig is placed with an interval of 200 μm. Then, the wafer 14 is placed on it. This second lower jig is provided with a wafer guide groove having a depth of 50 μm, and the cleavage portion including the scribe portion of the wafer 14 has the above-mentioned 200 μm.
It is arranged so that it becomes the center of the interval. Then, the second upper jig 18 (crimping plate) is placed and fixed with screws. The second upper jig is also spaced by 200 μm, and is arranged so that the cleavage portion including the scribe portion of the wafer 14 is exposed after fixing.

Next, the wafer 14 fixed to the second jig
Was taken out from the first jig 16 and entered the petri dish (N
It is transferred to a H ₄ ) ₂ S _x aqueous solution, and a cleavage blade is cleaved on the scribe portion of the wafer 14 to separate it into two laser bars. Here, the end face newly formed by cleavage is subjected to sulfide treatment immediately after cleavage, and is not exposed to oxygen in the air. Further, the laser bar is still fixed to the second jig even after the cleavage.

After the sulfide treatment is completed, the laser bar is fixed to the second jig and loaded into a sputtering device or the like.
₄ ) Al ₂ O on the end face formed by cleavage in ₂ S _x aqueous solution
An end face protection and antireflection film such as ₃ is formed. CO
The passivation of the end face on the light emitting side where the end face deterioration due to D easily occurs is completed. Further, the laser bar was removed from the jig, and Al ₂ O ₃ / α-Si / was attached to the other end face.
An end face protective and highly reflective film such as Al ₂ O ₃ / α-Si is formed. After that, the laser bar is cleaved into individual lasers to obtain laser chips.

A semiconductor laser manufactured by the passivation method of the end face of the semiconductor laser of the present invention has a COD of 500 mW or more.
Was showing the level. On the other hand, a semiconductor laser according to the conventional passivation method that does not perform sulfide treatment or that performs sulfide treatment after cleavage in air shows a COD level of 400 mW or less, confirming the effect of the passivation method according to the present invention. it can.

Second Embodiment As in the first embodiment, the process is performed until the wafer 14 is fixed to the second jig 17. This wafer was transferred to a glove box in a nitrogen atmosphere together with a container containing the (NH ₄ ) ₂ S _x aqueous solution, a cleavage blade was cleaved on the scribe part of the wafer 14 to separate it into two laser bars, and immediately (NH ₄ ) ₂ S
_x Put in aqueous solution. The oxygen concentration in this glove box is controlled to be 1 ppm or less. Here, the end face newly formed by cleavage is not exposed to oxygen in the air after cleavage, and is subjected to sulfide treatment. Hereinafter, Example 1
Passivate the end face in the same manner as in. The semiconductor laser produced by the passivation method for the end face of the semiconductor laser according to the second embodiment of the present invention also exhibits a COD level of 500 mW or higher, which confirms the effect of the passivation method according to the present invention. In addition, the end surface treatment liquid is P ₂ S ₅ /
The same effect can be obtained by using an aqueous solution of (NH ₄ ) ₂ S, Na ₂ S, K ₂ Se.

[0022]

According to the passivation method of the end face of the semiconductor laser according to the present invention, unlike the conventional passivation method of the end face of the semiconductor laser, the step of cleaving in air is not included, and the passivation method is performed in an oxygen-free atmosphere or in the end face treatment liquid. Cleavage is performed so that sulfide treatment can be performed before oxidation, so that treatment without oxide residue is possible, and a highly reliable high-power semiconductor due to reduction of surface level and reduction of COD level A laser can be realized.

In the passivation method of the end face of the semiconductor laser according to the present invention, the cleavage of the semiconductor laser in the end face treating liquid can be performed while being fixed to the jig having a certain weight, so that the semiconductor laser wafer is exposed in the solution. Cleavage at a predetermined position is possible without moving. Furthermore, the laser bar is fixed to the jig even after the cleavage, and it is possible to install the end face protective material as it is in the device for forming the end face protective material, and it is easy to handle in the sulfide solution. It is possible to provide a passivation method for an end face of a semiconductor laser.

The above embodiment relates to a semiconductor laser having a wavelength band of 0.8 to 1 μm or more in which an InGaAs / GaAs strained quantum well layer laminated on a GaAs substrate is used as an active layer, but the same effect is obtained. It is also effective in a semiconductor laser having an active layer of GaAs / AlGaAs or InGaP laminated on the top.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a sectional view of an epi structure of a semiconductor laser according to an embodiment of the present invention.

FIG. 3 is a diagram showing a jig for passivating an end face of a semiconductor laser according to an embodiment of the present invention.

[Explanation of symbols]

1 n ⁺ -GaAs substrate 2 n-GaAs buffer layer 3 n-AlGaAs clad layer 4 AlGaAs guide layer 5 AlGaAsSCH layer 6 InGaAs strained quantum well active layer 7 AlGaAsSCH layer 8 AlGaAs guide layer 9 p-AlGaAs clad layer 10 p ⁺ -GaAs Contact layer 11 Insulating film 12 p electrode 13 n electrode 14 Semiconductor laser wafer 15 Cleaving scribing 16 First jig (positioning table) 17 Second lower jig (fixing plate) 18 Second upper jig (crimping plate)

Claims (7)

[Claims] 1. A first step of cleaving a semiconductor laser in the process of manufacture, in which at least one end face is not formed, in an atmosphere containing no oxygen, and a first step in which the semiconductor laser is placed in the atmosphere and the surface level of the semiconductor laser is set. A second step of treating the end face formed in the first step with a treatment liquid having an action of suppressing the occurrence of the above, and a second step of coating the end face treated in the second step with an end face protective material. A method of passivating an end face of a semiconductor laser, comprising the step of 3. 2. A first step of cleaving a semiconductor laser in the process of manufacture, in which at least one end face is not formed, in a treatment liquid having an action of suppressing generation of a surface level of the semiconductor laser, and the first step. A passivation method for an end face of a semiconductor laser, comprising a second step of covering the end face formed in the first step with an end face protective material. 3. The method of passivating an end face of a semiconductor laser according to claim 2, further comprising a step of fixing the semiconductor laser to a jig before the first step. 4. The passivation method for an end face of a semiconductor laser according to claim 3, wherein in the step of coating the end face protection material, the end face protection material is coated while the jig is mounted. 5. A pair of fixing plates (17) having at least one end face not formed and forming a recess for dropping the semiconductor laser in the process of manufacture, and a pair of pressing plates for fixing the semiconductor laser to the fixing plate (17). A jig comprising a crimping plate (18) and a positioning base (16) having a groove for accommodating the pair of fixing plates (17) separately at an interval required for cleavage. 6. The passivation method for an end face of a semiconductor laser according to claim 3, wherein the jig according to claim 5 is used. 7. The passivation method for an end face of a semiconductor laser according to claim 1, wherein the treatment liquid is an (NH ₄ ) ₂ S _x aqueous solution.