JP2650769B2 - Method of manufacturing semiconductor laser device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an AlGaAs-based edge-emitting semiconductor laser device.

(Prior Art) A semiconductor laser device of AlGaAs type or the like has been widely used as a light source of an optical disk device or the like. When a semiconductor laser device is used as a light source of a writable write-once optical disk device or an erasable rewritable optical disk device, it is required to have high reliability even in a high light output state of 40 to 50 mW. . When used as a light source for excitation of a solid-state laser device such as a YAG laser,
High output of W or more is required.

(Problems to be Solved by the Invention) However, in a comparatively high-power semiconductor laser device currently in practical use, the reliability is inversely proportional to the fourth power of the light output when compared with devices having the same structure. Have been reported. That is, it has been very difficult to increase the light output while maintaining high reliability.

The main cause of deterioration of the semiconductor laser device in high-power operation is end face deterioration. This is because the light emission end face has a high light density and generates heat locally at the end face. The mechanism of this heat generation will be described with reference to FIGS. 11 and 12.

FIGS. 11 (a) and 11 (b) schematically show the energy band structure near the surface due to the surface level generated when the (110) plane of n-type and p-type GaAs is slightly oxidized, respectively. FIG. In both n-type and p-type cases,
The majority carriers accumulate near the surface, so-called accumulation layer 1
It can be seen that is formed.

In general, it is known that the surface level of a semiconductor bends the energy band near the surface. The bending is performed by forming the storage layer 1 as shown in FIGS. 11 (a) and 11 (b). In addition to the above, as shown schematically in FIGS. 12 (a) and (b), the minority carriers gather near the surface and the majority carriers are moved away from the surface, resulting in a local inversion of the conductivity type. 2 may be formed. Whether the accumulation layer 1 or the inversion layer 2 is formed is determined by the magnitude relation between the surface state and the Fermi level of the semiconductor. In the case of GaAs, either the n-type or the p-type The storage layer 1 is also formed in the above.

The electrons and holes trapped in the surface state Es are released in a short relaxation time, and the energy is released as heat. The electrons or holes are newly trapped in the vacant surface level, the same process is repeated, and heat is continuously released.

During the repetition of the above process, heat released from the surface level is concentrated on the semiconductor end face, and the heat generated reduces the energy band gap, further increases the number of minority carriers due to light absorption, and increases the surface level. The heat generation is further increased via.
By this process, the temperature of the semiconductor surface rises and eventually reaches the melting point, and the end face is destroyed.

In the case of GaAs, a storage layer is formed, but other materials,
For example, in AlGaAs, an inversion layer may be formed. In this case, although majority carriers are trapped in the surface state, the end face is destroyed through the same process as in the case of the accumulation layer. Further, in the case of a semiconductor laser device used in a high injection state, heat generation due to surface states has become a more serious problem.

As a method for preventing the end face deterioration due to the heat generation of the end face as described above, a structure in which a window region is formed near the end face has been proposed. This is to provide a region that is transparent to laser light near the end face, thereby eliminating light absorption at the end face and suppressing heat generation due to light absorption. However, in such a configuration, there is a problem that the process of forming the window region is very complicated, and it is very difficult to form a waveguide near the end face.

In order to improve the characteristics of the interface in the MIS structure using GaAs, Extended Abstrac
ts of the 20th Conference on Solid State Devices a
There is a method proposed in nd Materials, Tokyo, (1988) pp. 263-266. This makes the surface of GaAs (NH ₄ ) ₂
By treating with an S aqueous solution, the oxide film formed on the GaAs surface is removed in the air, and instead, GaS is attached. Here, by forming the layer made of GaS, the surface state due to the oxide film is reduced.

However, with respect to the end face of the optical element, especially the end face of the AlGaAs semiconductor laser device, improvement by the above-described surface treatment has not been attempted so far. this is,
This is because Al was considered to be a very active substance, and its acidic film was stable and could not be removed.

Accordingly, an object of the present invention is to provide a method for manufacturing an AlGaAs semiconductor laser device having a configuration in which surface levels due to oxides on a light emitting end face can be suppressed and the end face is hardly destroyed even in a high output state. Is to provide.

(Means for Solving the Problems) The manufacturing method of the present invention is directed to a method of manufacturing an edge-emitting semiconductor laser device having an AlGaAs active layer and having a protective film formed on an end face. And the step of forming the protective film thereafter, thereby achieving the above object.

Further, the solution containing sulfur is (NH ₄ ) ₂ S stock solution, (N
It may be selected from the group consisting of H ₄ ) ₂ S _x stock solution, (NH ₄ ) ₂ S aqueous solution, and (NH ₄ ) ₂ S _x aqueous solution.

Further, when the sulfur-containing solution has a sulfur concentration of Xmol /, the time for treating the end face with the sulfur-containing solution may be 1.5 / X seconds or more.

Further, the end face may be formed by cleaving the wafer in the solution containing sulfur, and thereafter, the end face may be treated with the solution.

Further, the protective film may be formed by a resistance heating evaporation method using a low melting point material.

Further, the low melting point material may be selected from the group consisting of MgF ₂ , SiO, SiO ₂ , CaF ₂ and NaF.

Further, the protective film may be formed at a growth rate of 10 ° / sec or less by an electron beam evaporation method.

EXAMPLES Hereinafter, the present invention will be described with reference to examples. The semiconductor laser device of the following embodiment has the same basic structure as that of a known end-emitting type device conventionally used, and a film mainly composed of sulfur is formed on the end surface. The feature is that an end face protective film is formed on the sulfur-based film. Therefore, in the following description, the formation process and structure of the end face will be mainly described.

FIG. 1 is a perspective view schematically showing the vicinity of an end face on the front side of the semiconductor laser device of the first embodiment. The manufacturing process of this embodiment will be described.

As shown in FIG. 2 (a), an AlGaAs
A laminated structure 12 including an active layer 16 was grown, and resistive electrodes 13 and 14 were formed on both surfaces.

Next, the bar is cleaved by a known cleavage method so as to have a predetermined resonator length to form a bar 15 in which a plurality of resonator units are connected in a direction perpendicular to the resonator direction (FIG. 2 (b)). )).

Immediately after cleavage, the bar 15 is replaced with a 10% aqueous solution of (NH ₄ ) ₂ S 20
And immersed at room temperature for 3 minutes to perform surface treatment of the cleavage plane (FIG. 2 (c)). As a result, a film 18 containing sulfur was formed on the end face.

Thereafter, the bar 15 is washed with water and then dried, and a reflection film 17 made of an Al ₂ O ₃ film having a reflectance of 4% made of Al ₂ O ₃ film is formed on the end surface on the back side, and Al is coated on the end surface on the back side by a usual electron beam evaporation method. A reflective film having a reflectivity of 95% and having a multilayer structure of ₂ O ₃ and amorphous Si was formed. Thereafter, the bar 15 was further cleaved to obtain a semiconductor laser device.

FIG. 3 shows an injection current versus light output characteristic (curve A) of the semiconductor laser device obtained through the above steps. For comparison, an injection current versus light output characteristic of a semiconductor laser device having the same configuration as that of the related art, that is, having a reflection film formed directly on the end face after cleavage is shown by a curve B. In this conventional example, the device was degraded due to the end face breakdown at an optical output of about 200 mW, whereas in the present embodiment, a maximum optical output of about 600 mW was obtained, and at that time, the end face breakdown occurred. It turns out there is no.

The above facts, in order to confirm that this is due to the reduction of surface states caused by the oxide film was conducted actually measured surface state density, a semiconductor laser device of the present embodiment from about 10 ⁸ to It was confirmed to be 10 ⁹ cm ^-2 · eV ^-1 . Ga
When the same treatment was performed for the As-based semiconductor laser device, the value of 10 ¹¹ to 10 ¹² cm ^-2 eV ^-1 was the smallest, and the effective reduction of the surface state as described above was not seen. Was.

Therefore, it is presumed that the above-mentioned large effect of reducing the surface state density is caused by the presence of Al, contrary to what has conventionally been considered.

As described above, in order to improve the end face breakdown output of the semiconductor laser device, it is important that the solution used for the end face treatment contains sulfur.

As described above, in the first embodiment, the protective film 17 made of the Al ₂ O ₃ film was formed on the end face by the ordinary electron beam evaporation method. However, even in a semiconductor laser device having an end face protective film 17 formed by an electron beam evaporation method or a sputtering method, even if the semiconductor laser device is subjected to a surface treatment with an (NH ₄ ) ₂ S solution, the improvement of the high output characteristics is not achieved. Some were not high enough. This is because the natural oxide film is removed by the surface treatment with the (NH ₄ ) ₂ S solution, and the formed sulfur-containing film 18 is formed during the process of forming the protective film 17 by the electron beam evaporation method or the sputtering method. It is considered that this may cause deterioration.

Protective film by electron beam evaporation or sputtering
When forming 17, secondary electrons and ions may be generated during these steps and may collide with the laser light emission side end face. In this case, the sulfur is released from the sulfur-containing film 18 formed on the end face on the laser light emission side, and the semiconductor surface of the portion from which the sulfur is released is exposed. The semiconductor surface exposed at the laser light emission side end face may be oxidized again by a trace amount of oxygen existing in the vapor deposition apparatus.

Next, a second embodiment in which the film 18 containing sulfur is not deteriorated during the process of forming the protective film 17 will be described.

In the present embodiment, after treating the laser light emitting side end face of the bar 15 in the same manner as in the first embodiment, the bar 15 is placed in the chamber of the resistance heating evaporation apparatus to form the protective film 17 on the end face. I set it.

Then, in the chamber, carrying the MgF ₂ granular crystals Mo
The board was heated to a temperature of about 1600 ° C. to deposit MgF ₂ on the laser emitting end face of the bar 15. Thus, the protective film 17 made of MgF ₂ was formed on the end face of the bar 15 on the laser light emission side.

Since MgF ₂ (melting point 1265 ° C.) is a material having a relatively low melting point, a high-quality end face protective film 17 could be formed by a vacuum deposition method using a resistance heating method. Similar to MgF ₂ , SiO, SiO ₂ , CaF ₂ , NaF, ZnS, and the like, which have a relatively low melting point and become a high-quality end face protective film 17 by a resistance heating type deposition method, can be used.

During the process of forming the end face protective film 17 using the resistance heating type vacuum deposition method, unlike the process using the electron beam evaporation method, secondary electrons do not collide with the end face and the sputtering method is used. Unlike during the process, ions did not collide with the end face.

Therefore, when the end face protective film 17 was formed by using a resistance heating type vacuum evaporation method, the sulfur-containing film 18 on the end face was not damaged. In order to form the end face protective film 17 using a resistance heating type vacuum deposition method, it is preferable that the material to be deposited has a relatively low melting point. In particular, the melting point of the protective film material is preferably about 2000 ° C. or less. In this specification, a material having a melting point of 2000 ° C. or lower is referred to as a low melting point material.

After the semiconductor laser device thus obtained and the end face treatment were performed, the Al ₂ O ₃ protective film 1 was formed by a sputtering method.
The result of a comparative experiment with a semiconductor laser device (Comparative Example) in which 8 is formed on the end face will be described.

First, the relationship between light output and cross-sectional degradation was compared. As a result, in the comparative example, the end face was destroyed when the optical output was 180 mW. On the other hand, in the semiconductor laser device of the present example, even during operation at an optical output of 300 mW, stable laser oscillation was maintained without occurrence of end-face destruction.
After the semiconductor laser device of the present embodiment was left for a long time, the same results were obtained even when the above experiment was performed.

Next, after leaving the semiconductor laser device of the present example and the comparative example for 6 months in an air atmosphere, they were inserted into a chamber,
The end face protective film 17 was removed by Ar ⁺ ion sputtering, and the state of chemical bonding at the interface between the semiconductor crystal and the protective film was analyzed by X-ray photoelectron spectroscopy (XPS). As a result, at the interface between the semiconductor crystal of the present embodiment and the protective film 17, Ga and As
It was found that there was no bond between oxygen and oxygen.

On the other hand, at the interface between the semiconductor crystal of the comparative example and the protective film, Ga
It was also found that a bond between As and oxygen occurred. This is because the film containing sulfur on the end face was damaged by charged particles during the step of forming the end face protective film of the comparative example, and oxygen was trapped on the temporarily exposed semiconductor surface. It is.

In the semiconductor laser device of the present embodiment, since the protective film 17 made of a low-melting-point material is formed on the film 18 containing sulfur by resistance heating evaporation, sulfur on the end face is generated during the evaporation process. There was no peeling from the end face. For this reason, in the semiconductor laser device of the present embodiment, even if the high-power operation is performed for a long period of time, oxidation is prevented from progressing at the interface between the protective film 17 and the semiconductor crystal. Therefore, in the semiconductor laser device of this embodiment, the increase in the number of non-radiative recombination centers was suppressed, so that the deterioration of the end face was suppressed, and stable laser oscillation with high output could be performed for a long time.

Next, a third embodiment will be described with reference to FIG.

In the same manner as in the first and second embodiments, the end face of the laser light emitting side, which is the cleavage plane of the bar 15, is processed to form a sulfur-containing film 18 on the end face. In order to form the protective film 17 on the end face, the bar 15 was set in a chamber of a resistance heating evaporation apparatus. Next, oxygen (pressure 1 ×
In a chamber into which 10 ⁻² Pa) was introduced, the Mo board on which the SiO granular crystals were placed was heated, and the temperature was raised to about 1700 ° C. or higher, thereby evaporating the SiO. Due to the reaction between SiO and oxygen in the atmosphere, a protective film made of SiO ₂ is formed on the end face.
17a was formed (see FIG. 4). The thickness of the protective film 17a made of SiO _{2 was set} to be λ / (2n) Å. Then, Al ₂ O _{3 is} deposited on the protective film 17a by electron beam evaporation.
A protective film 17b made of O ₃ was formed (see FIG. 4). The thickness of the protective film 17b was λ / (4n) Å. Thus, the reflectance of the end face on the laser light emission side was set to 5%.

Since SiO is also a material having a relatively low melting point, a high-quality end face protective film can be formed by a resistance heating type vacuum deposition method without damaging a sulfur-containing film.

In this embodiment, the protective film 17b is formed on the protective film 17a by the electron beam evaporation method, but the film 18 containing sulfur is covered by the protective film 17a formed by the resistance heating evaporation method. It was not damaged by scattered electrons by electron beam evaporation.

Note that the end face protective film 17 is not limited to the case where the end face protective film 17 is composed of two layers including the protective film 17a and the protective film 17b, and may be a multilayer film composed of three or more layers.

As described above, in the second and third embodiments, after the end face treatment, the protective film made of the low melting point material was formed on the laser light emitting side end face by the resistance heating type vapor deposition method. However, when a material having a relatively high melting point, for example, Al ₂ O ₃ (melting point: 2046 ° C.) is used as the material of the protective film, it is difficult to form the film by the resistance heating evaporation method.

A fourth embodiment in which a protective film made of a material having a relatively high melting point is formed by an electron beam evaporation method will be described below.

In this embodiment, after performing the end face treatment with the sulfur-containing solution in the same manner as the other embodiments, the film formation rates were each set at 5 ° / se.
A formed as c, 10Å / sec, 12Å / sec, and 15Å / sec
A semiconductor laser device having an l ₂ O ₃ protective film was manufactured.

FIG. 5 shows the relationship between the current versus light output characteristics of the semiconductor laser device of the present embodiment and the film formation rate. In the figure, H, I,
The lines indicated by J and K correspond to the light output characteristics of the semiconductor laser device having the protective films with the film formation rates of 5 ° / sec, 10 ° / sec, 12 ° / sec and 15 ° / sec, respectively. I have.

FIG. 6 is a graph showing the relationship between the maximum light output and the protective film formation rate. For comparison, the maximum light output of the semiconductor laser device for which the end face processing has not been performed is indicated by a broken line.

As can be seen from FIGS. 5 and 6, as the protective film formation rate increases, the maximum light output decreases and approaches the maximum light output of the semiconductor laser device for which the end face processing has not been performed.

This is because, when the emission amount of the electron beam is increased in order to increase the formation rate of the protective film, a large number of high-energy scattered electrons such as secondary electrons are generated, and the scattered electrons cause the laser light emission of the bar 15. This is considered to be because the sulfur-containing film 18 formed on the end face is damaged.

As can be seen from FIG. 6, the effect of this damage on the maximum light output is remarkable when the protective film formation rate is 10 ° / sec or more. However, the protective film formation rate is 10Å / sec
If it is below, a high maximum light output of 540 mW or more was obtained. This is considered to be because if the Al ₂ O ₃ film formation rate is 10 ° / sec or less, the sulfur-containing film formed on the laser beam emitting end face of the bar 15 is hardly damaged.

Further, an experiment similar to the above experiment was performed on an end surface different from the end surface on the laser light emission side. As a result, the Al ₂ O ₃ film and the Si film on the end surface on the side different from the end surface on the laser light emission side
It has been found that the relationship between the film formation rate and the light output characteristics does not have the above-described dependence.

Therefore, in order to obtain a high maximum light output, at least the formation rate of the protective film on the end face on the laser light emission side should be 10Å / s.
It is preferably set to ec or less.

In each of the above embodiments, the surface treatment was performed using an aqueous solution of (NH ₄ ) ₂ S. However, the surface treatment may be performed using an undiluted solution instead of an aqueous solution, or using another solvent. It is also possible.

A stock solution of (NH ₄ ) ₂ S and a 10% aqueous solution thereof (N
Fifth Embodiment A description will be given of a fifth embodiment in which the end face treatment is performed using each of the stock solution of H ₄ ) ₂ S _x and its 10% aqueous solution. Where (NH
₄ ) ₂ S _x is a mixture of (NH ₄ ) ₄ S and (NH ₄ ) ₂ S _2, and x indicating the composition ratio of sulfur is a real number of 1 or more and 2 or less.

FIG. 7 shows a stock solution of (NH ₄ ) ₂ S and a 10% aqueous solution, (NH ₄ )
FIG. 9 is a graph showing the end surface breakdown output (mW) of the semiconductor laser device of the present embodiment in which the end surface treatment was performed using each of the ₂ S _x stock solution and the 10% aqueous solution and the semiconductor laser device in which the end surface was not processed (comparative example) is there.

As can be seen from this figure, the stock solution of (NH ₄ ) ₂ S and 10%
The end face breakdown output of the semiconductor laser device subjected to the end face treatment using the aqueous solution, the undiluted solution of (NH ₄ ) _{2 Sx} , and the 10% aqueous solution was significantly higher than the end face breakdown output of the semiconductor laser device of the comparative example.

The thickness of the AlGaAs active layer of the semiconductor laser device of this embodiment and the semiconductor laser device of the comparative example is larger than the thickness of the AlGaAs active layer of the semiconductor laser device shown in the experimental results shown in FIG. Therefore, in the semiconductor laser devices of this embodiment and the comparative example, the light density is higher and the end face breakdown output is lower than that of the semiconductor laser device showing the experimental results shown in FIG.

In the present embodiment, a stock solution of (NH ₄ ) ₂ S and a 10% aqueous solution, (N
The end face treatment of the semiconductor laser device was performed using an undiluted solution of H ₄ ) ₂ S _x and a 10% aqueous solution, but the (NH ₄ ) ₂ S solution and the (NH ₄ ) ₂ S
Similar effects can be obtained not only when the _x solution is used but also when a sulfur alkali metal compound solution is used. That is, the material used for the surface treatment is not particularly limited as long as a film containing sulfur can be formed on the end face of the semiconductor laser device.

Next, a description will be given of an experiment conducted to determine the relationship between the sulfur concentration of a sulfur-containing solution and the processing time required for end face treatment with the solution, and the results thereof.

In the experiment, the sulfur concentration was 0.015 mol /, 0.15 mol /,
And 0.5 mol / of each solution (NH ₄ ) ₂ S solution).
After immersing the As crystal for a predetermined time, the AlGaAs crystal surface was evaluated by Auger electron spectroscopy. In addition, the solution temperature at the time of immersion was about room temperature.

FIG. 8 shows the results obtained from the Auger electron spectrum.
5 is a graph showing the relationship between the Auger signal intensity of oxygen existing on the GaAs crystal surface and the immersion time. In the graph, the relationship when the sulfur concentration of the used solution is 0.015 mol / is shown by line D, the relationship when it is 0.15 mol / is shown by line E, and the relationship when it is 0.5 mol / is shown by line F.

As shown in this graph, at any concentration of the solution, the longer the immersion time, the lower the Auger signal intensity of oxygen, and approached the background signal level.

FIG. 9 shows the relationship (line G) between the immersion time (time required for oxygen removal) until the Auger signal intensity of oxygen reaches the background level and the sulfur concentration of the solution, obtained from the above experimental results. It is a logarithmic graph.

In the graph, it is an alkali metal compound solution of sulfur
The relationship (dashed line) between the immersion time until the Auger signal intensity of oxygen reaches the background level and the sulfur concentration of the solution when an aqueous solution of Na ₂ S is used as the processing solution is also shown.

As can be seen from FIG. 9, the immersion time until the Auger signal intensity of oxygen reaches the background level and the sulfur concentration of the solution are almost inversely proportional. This means
This indicates that oxygen existing as an oxide film or the like on the AlGaAs crystal surface is removed from the AlGaAs crystal surface by reacting with sulfur in the solution as shown in the following reaction formula (1).

Oxide + Sulfur → Sulfide + Oxygen (1) The rightward reaction rate of the above reaction is represented by the following equation (2).

−d [oxide] / dt = K · [oxide] · [S] (2) where [oxide] is the oxide concentration on the AlGaAs crystal surface, [S] is the sulfur concentration of the solution, and K is The rate constant, t, is the time elapsed from the start of immersion. The left side of the above equation (2) is a time differential value of [oxide], and shows a value at a certain time of a rate at which the oxide on the AlGaAs crystal surface is removed from the surface.

[Oxide] is obtained by solving the above differential equation (2) as a relationship of time t as shown in the following equation (3).

[Oxide] = [Oxide] ₀ · exp− ^{K [S] t} (3) Here, [Oxide] ₀ is [Oxide] at the start of immersion (t = 0). Since the total amount of sulfur in the solution is much larger than the total amount of oxide on the surface of the AlGaAs crystal, [S] was treated as a time-independent constant when solving the differential equation (2).

From the above equation (3), the time t _c required for [oxide] to decrease by 99% of [oxide] ₀ is shown in the following equation (4).

t _c = (ln100) / (K · [S]) (4) The above equation (4) indicates the following. That is, Al
The time required for removing 99% of the AlGaAs crystal surface from the oxygen existing as an oxide film on the GaAs crystal surface by reacting with the sulfur in the solution is inversely proportional to the sulfur concentration in the solution. That's what it means. This is consistent with the experimental results shown in the graph of FIG.

When the above equation (4) was fitted to the function (line G) shown in the graph of FIG. 9, the following equation (5) was obtained.

t _c = 1.5 / [S] (5) Here, the unit of t _c is [sec], and the unit of [S] is [mol /
], And the unit of 1.5 is [sec · mol /].

When a solution having a sulfur concentration of 0.015 mol / is used, t _c = 100 seconds is obtained from the above equation (5). Therefore, when using a solution having a sulfur concentration of 0.015 mol /, if the end face treatment is performed only for a time shorter than 100 seconds, the AlGaAs on the end face
The oxide film present on the crystal surface cannot be completely removed. That is, in order to remove most of the oxide film present on the AlGaAs crystal surface, it is necessary to perform the end face processing for a time longer than _tc seconds shown in the above equation (5).

Thus, from the above experimental results and their considerations,
The immersion time required to remove most of the oxide film present on the GaAs crystal surface was obtained.

Based on this, by treating the end face with an appropriate treatment time according to the sulfur concentration of the solution to be used, insufficient removal of the end face oxide film due to shortage of the end face treatment time does not occur, and more than the required time Waste of time-consuming edge processing is eliminated.

As can be seen from the graph of FIG. 9, the oxide film on the surface of the AlGaAs crystal is also removed when Na ₂ S is used as the edge treatment solution in the same manner as when the (NH ₄ ) ₂ S solution is used. . However, the semiconductor laser device that has been subjected to the end face treatment using the (NH ₄ ) ₂ S solution or the (NH ₄ ) ₂ S _x solution is superior to the semiconductor laser device that has been subjected to the end face treatment using the Na ₂ S solution. Demonstrated reliability. Among the sulfur-containing solutions, the (NH ₄ ) ₂ S solution and the (NH ₄ ) ₂ S _x solution are particularly excellent end-face treatment solutions from the viewpoint of the reliability of the semiconductor laser device.

In any of the above embodiments, after the wafer was cleaved in the air, the cleaved surface was immersed in a 10% aqueous solution of (NH ₄ ) ₂ S 20 to treat the light-emitting-side end surface. . In this case, in order to cleave the wafer in the atmosphere, the cleavage plane immediately came into contact with the atmosphere after the cleavage.

A sixth embodiment in which cleavage is not performed in the atmosphere will be described below with reference to FIG.

After forming the laminated structure 12 on the substrate 11 in the same manner as in the other examples (10th (a)), a wafer of a 10% aqueous solution 20 of (NH ₄ ) ₂ S is immersed, and tweezers 40 are used. Then, the wafer was cleaved in an aqueous solution 20 to form a bar 15 having a predetermined resonator length (FIG. 10 (b)). After the cavity end face of the semiconductor laser device was formed by cleavage in the aqueous solution 20, the bar 15 was immersed in the aqueous solution for 3 minutes to perform surface treatment of the cleavage plane. Thus, the cleaved end face is
It was covered with a film containing sulfur without contacting the atmosphere containing oxygen.

Thereafter, the bar 15 was washed with water and dried (FIG. 10 (c)), and thereafter, a 4% reflectivity made of an Al ₂ O ₃ film was formed on the laser light emission side end face by a normal electron beam evaporation method. A reflective film was formed. Also, Al ₂ O ₃ and amorphous Si
A reflective film having a reflectivity of 95% and having a multilayer structure was formed.
Thereafter, the bar 15 was further cleaved to obtain a semiconductor laser device.

When the surface state density was measured, it was confirmed that the density was about 10 ⁷ cm ⁻² · eV ⁻¹ in the semiconductor laser device of this example. When the same measurement was performed for the comparative example in which the wafer was cleaved in the air, the result was about 10 ⁹ cm ^-2 · eV ^{-1 which} was the smallest, and the effective surface state density as described above was No reduction was seen.

As described above, in the present embodiment, the natural oxidation of the cleavage plane by the air could be prevented by cleaving the wafer in the (NH ₄ ) ₂ S aqueous solution. For this reason, the surface treatment of the cleavage plane in the (NH ₄ ) ₂ S aqueous solution was effectively performed, and the surface order density caused by the oxide film was reduced.

(Effect of the Invention) As described above, according to the present invention, the film containing sulfur is made of AlGa
Since it is formed on the end face of the semiconductor laser device having the As active layer, the surface level of the end face is greatly reduced. Therefore, deterioration due to heat generation at the light emitting end face due to surface recombination can be effectively suppressed, and the output of the AlGaAs semiconductor laser device can be increased with high reliability.

Further, by treating the end face with a solution containing sulfur, the end face covered with the film containing sulfur and having a small number of surface states can be easily formed. By optimizing the type and method of forming the protective film formed on the end face, a semiconductor laser device excellent in high output characteristics can be manufactured with high yield without damaging the sulfur-containing film.

In addition, by treating the end face with an appropriate treatment time according to the sulfur concentration of the solution to be used, insufficient removal of the end face oxide film due to shortage of the end face treatment time does not occur, and the end face treatment takes more time than necessary. The waste of doing is eliminated.

Further, by performing cleavage of the wafer in a solution containing sulfur, oxidation of the end face is more effectively suppressed, and a highly reliable semiconductor laser device with improved output can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing the vicinity of an end face on the laser light emission side of the apparatus of the first embodiment, and FIGS. 2 (a) to 2 (c) are perspective views for explaining manufacturing steps of the embodiment. FIG. 3 is a diagram showing injection current versus light output characteristics of the semiconductor laser device of the embodiment, FIG. 4 is a perspective view schematically showing the vicinity of an end face on the laser light emission side of the device of the third embodiment, FIG. FIG. 5 is a graph showing the relationship between the current versus light output characteristics of the device of the fourth embodiment and the film formation rate, FIG. 6 is a graph showing the relationship between the maximum light output and the protective film formation rate of the embodiment, FIG. 7 is a graph showing the end face breakdown output of the semiconductor laser device of the fifth embodiment, FIG. 8 is a graph showing the relationship between the Auger signal intensity of oxygen and the immersion time at the end face of the fifth embodiment, Figure 9 shows the immersion time and solution until the Auger signal intensity of oxygen reaches the background level. Graph showing the relationship between the sulfur concentration, the
FIGS. 10 (a) to 10 (c) are cross-sectional views for explaining the manufacturing method of the sixth embodiment, and FIGS. 11 (a) and 11 (b) each show n
FIGS. 12 (a) and 12 (b) schematically show a state in which a carrier accumulation layer is formed on the surfaces of n-type and p-type GaAs. FIGS. It is a figure which shows the state currently performed typically. 11 ... Semiconductor substrate, 12 ... Laminated structure, 13, 14 ... Electrode,
15 ... bar, 16 ... active layer, 18 ... film containing sulfur, 17,
17a, 17b: protective film, 20: (NH ₄ ) ₂ S aqueous solution.

Continued on the front page (72) Inventor Hiroshi Hayashi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Nobuyuki Miyauchi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72 Inventor Morino Yano 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside Sharp Corporation (72) Inventor Takehiro 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Sharp Corporation (72) Inventor Sasaki Kazuaki 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Sharp Corporation (72) Inventor Akihiro Matsumoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Masaki Kondo Osaka-shi, Osaka 22-22 Nagaike-cho, Abeno-ku, Sharp Corporation (72) Inventor Saburo Yamamoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation Proceedings of the Physical Society of Japan Academic Lectures 3rd volume 28p − G-9 p. 899 Jpn. J. Appl. Phys. 29 [II] (1990) p. 2473−2476

Claims (7)

(57) [Claims] In a method for manufacturing an edge-emitting semiconductor laser device having an AlGaAs active layer and a protective film formed on an end face, a step of treating the end face with a sulfur-containing solution, and thereafter A method for manufacturing a semiconductor laser device including a step of forming the protective film. 2. The method according to claim 1, wherein the sulfur-containing solution is (NH ₄ ) ₂ S stock solution,
_{2. The} method for manufacturing a semiconductor laser device according to claim 1, wherein the solution is selected from the group consisting of an (NH ₄ ) ₂ S _x stock solution, an (NH ₄ ) ₂ S aqueous solution, and an (NH ₄ ) ₂ S _x aqueous solution. 3. The semiconductor laser device according to claim 1, wherein when the sulfur concentration of the sulfur-containing solution is Xmol / l, the time for treating the end face with the sulfur-containing solution is 1.5 / X seconds or more. Manufacturing method. 4. The method for manufacturing a semiconductor laser device according to claim 1, wherein the formation of the end face is performed by cleaving the wafer in the solution containing sulfur, and thereafter, the end face is treated with the solution. 5. The method of manufacturing a semiconductor laser device according to claim 1, wherein said protection film is formed by a resistance heating evaporation method using a low melting point material. 6. The low melting point material is MgF ₂ , SiO, SiO ₂ , CaF
6. The method of manufacturing a semiconductor laser device according to claim 5, wherein the method is selected from the group consisting of ₂ and NaF. 7. The method of manufacturing a semiconductor laser device according to claim 1, wherein said protective film is formed by an electron beam evaporation method at a growth rate of 10 ° / sec or less.