JPH10308550A - Semiconductor laser element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form a stable edge protecting film by making the protecting film of the edge of a resonator to be an oxide film, which is formed by placing the cleavage plane of a wafer in oxygen atmosphere without exposing in atmospheric air after the wafer for a semiconductor laser element is cleaved in ultra-high vacuum atmosphere. SOLUTION: Cleavage is performed in ultra-high vacuum atmosphere. When the tip of a plate 42 for cleaving a laser bar 32 approaches a sample holder 31 and the plate 42 enters the lower side of the laser bar 32, the approaching of a straight-line guiding device 41 to the sample holder 31 is stopped. Then, the position of the sample holder an is lifted up, or the position of the straight- line guiding device 41 is lowered. Thereafter, when the laser bar 32 and the plate 42 are brought into contact, the laser bar 32 is cleaved. In the processing chamber, the cleaved laser bar 42 is separated, and the laser bar 32 remaining in the sample holder 31 is utilized as a reserver. At the cleaved surface of the laser bar 32, a natural oxide film and the clean surface without attached material and the like are exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device which suppresses deterioration of a cavity facet due to optical damage and realizes high-output stable operation.

[0002]

2. Description of the Related Art It is known that, in a semiconductor laser device formed of an AlGaAs-based or AlGaInP-based semiconductor material, a cavity end face is deteriorated (optical damage) with an increase in optical output. This optical damage is caused by a rise in the temperature of the cavity facet accompanying the high output operation of the semiconductor laser device. At the cavity end face, the laser light is absorbed via the surface level, and heat is locally generated. Then, due to this temperature rise, the forbidden band width near the end face is reduced, light absorption further increases, and the end face temperature rises. Due to this positive feedback loop, the end face of the resonator is finally melted, and the element is deteriorated.

Conventionally, in order to suppress light absorption at the cavity end face, various window structures for forming a material transparent to laser light on the cavity end face have been tried. For example, 1989
IE Journal of Quantum Electronics (IEEE, J. Quantum Electro
nics), Vol. 25, pp. 1495-1499, reports that a window structure for suppressing light absorption at the cavity facet can be used for patterning, selective etching, and buried regrowth of the cavity facet in the active region. Window structures formed by the process have been reported.

[0004]

In order to suppress optical damage, a protective film made of a dielectric material is usually formed on the end face of the resonator to suppress the reflectance of the end face of the resonator and promote new oxidation from the atmosphere. Restrained. However, since the conventional protective film forming method cleaves the laser wafer in the air to form the protective film, a natural oxide film is formed at the interface between the semiconductor cleavage surface and the dielectric. This natural oxide film is very unstable, forming complex surface states at the interface,
In addition, there are drawbacks such as generation of surface defects.

An object of the present invention is to provide a semiconductor device in which a stable end face protective film is formed on a cleaved end face of a semiconductor laser without forming an unstable natural oxide film in order to suppress optical damage to the end face of the resonator. It is to provide a laser element.

[0006]

According to the present invention, there is provided a semiconductor laser device having a protective film provided on an end face of a resonator, wherein the protective film is formed on a wafer for a semiconductor laser device in an ultra-high vacuum atmosphere. An oxide film formed by cleaving the wafer under the substrate and exposing the cleavage surface of the wafer to an oxygen atmosphere without exposing the wafer to an air atmosphere. The oxide film formed in this manner has substantially no surface state, improves the COD level of the semiconductor laser device, and can realize a semiconductor laser device having high output and high reliability.

Further, a semiconductor laser device according to the present invention is a semiconductor laser device having a protective film provided on an end face of a resonator, wherein the protective film is cleaved from a semiconductor laser device wafer in an ultra-high vacuum atmosphere. Thereafter, the oxide film is formed by heating the wafer under an oxygen atmosphere without exposing the cleavage plane of the wafer to an atmosphere in the air.

Further, the semiconductor laser device of the present invention is a semiconductor laser device having a protective film provided on an end face of a resonator, and the protective film is cleaved from a semiconductor laser device wafer in an ultra-high vacuum atmosphere. Thereafter, the oxide film is formed by irradiating light in an oxygen atmosphere without exposing the cleavage plane of the wafer to an air atmosphere.

In the method for manufacturing a semiconductor laser device according to the present invention, the wafer for the semiconductor laser device is cleaved in an ultra-high vacuum atmosphere, and the wafer is placed in an oxygen atmosphere without exposing the wafer to an air atmosphere. Forming an oxide film on the cleavage end face of the wafer.

Further, according to the method of manufacturing a semiconductor laser device of the present invention, a step of cleaving a wafer for a semiconductor laser device in an ultra-high vacuum atmosphere and heating the wafer in an oxygen atmosphere without exposing the wafer to an air atmosphere. Forming an oxide film on the cleavage end face of the wafer.

The method of manufacturing a semiconductor laser device according to the present invention comprises the steps of cleaving a wafer for a semiconductor laser device in an ultra-high vacuum atmosphere and irradiating the wafer in an oxygen atmosphere without exposing the wafer to an air atmosphere. Forming an oxide film on the cleaved end face of the wafer.

Further, in the method of manufacturing a semiconductor laser device according to the present invention, there is provided a step of cleaving a semiconductor laser device wafer in an ultra-high vacuum atmosphere, a step of irradiating gallium on a cleaved end face of the wafer, Forming a gallium oxide film by placing the film in an oxygen atmosphere.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. The semiconductor laser device 1 has a cleavage end face 2 formed by cleavage in a vacuum,
An oxide film 3 is formed on the cleavage end face 2 in a high-purity oxygen atmosphere. This oxide film can be formed by electron beam lithography (Nanotechno) reported recently.
(Kaishi et al., Vol. 3, p. 54, (1992), by Kasai et al.) are the same as those used as stable resist materials when forming ultrafine patterns on semiconductor substrates.

The cleavage end face 2 is formed in an ultra-high vacuum atmosphere. Conventionally, to fabricate a laser device, a laser wafer was cleaved in the air, and the cleaved surface was used as a cavity end face. However, in this method, an unstable natural oxide film was formed on the surface of the semiconductor cleaved surface, As described above, problems such as formation of complex surface levels at the interface and generation of surface defects or the like occur. Therefore, in order to prevent the formation of this natural oxide film, it is necessary to perform the cleavage in an ultra-high vacuum atmosphere. Here, the ultra-high vacuum is about 1 × 10 ⁻⁷ Torr
Refers to the following vacuum.

FIG. 2 is an overall view of an apparatus for manufacturing the semiconductor laser device of the present invention. This apparatus includes a processing chamber 21 for cleaving a laser wafer, a growth chamber 22 for forming a protective film on a cleavage end face, the processing chamber 21, and an exchange chamber 23 connecting the growth chamber 22. Each chamber is maintained in an ultra-high vacuum atmosphere on the order of 10 ⁻¹⁰ Torr, and is separated by a gate valve 24. The sample can be freely moved in the respective chambers by the first and second magnet feedthroughs 25 and 26.

FIG. 3 is a schematic view of a sample holder for cleaving a sample. The sample holder 31 is used by fixing a laser bar 32 having a plurality of laser elements connected in a bar shape in an upright state. The sample holder 31 is moved between the processing chamber 21, the growth chamber 22, and the exchange chamber 23 shown in FIG.
Each step of cleavage and formation of a protective film is performed.

Next, the cleavage procedure will be described. FIG.
Is a process drawing showing a cleavage procedure. This cleavage is performed in the processing chamber 21 in an ultra-high vacuum atmosphere. FIG. 4A is a diagram showing the positional relationship between the sample holder 31 to which the laser bar 32 before cleavage is fixed and the linear introducer 41 to which the plate 42 for cleaving the laser bar 32 is fixed at the tip. Before cleavage, the sample holder 31 and the straight line introducer 41 are separated from each other. Next, as shown in FIG. 4B, the linear guide 41 is inserted into a plate 42 for cleaving the laser bar 32.
So as to enter the lower side of the sample holder 31. The tip of the plate 42 for cleaving the laser bar 32 approaches the sample holder, and when the plate 42 enters the lower side of the laser bar 32, the approach of the linear introducer 41 to the sample holder 31 is stopped. Next, as shown in FIG. 4C, the position of the sample holder 31 is raised, or the position of the linear introducer is lowered. Then, when the laser bar 32 comes into contact with the plate 42, the laser bar 32 is cleaved. In the processing chamber 21, the cleaved laser bar 43 is separated, and the laser bar 32 remaining in the sample holder 31 is used as a laser element. Since the cleavage of the laser bar 32 was performed in an ultra-high vacuum atmosphere, a clean surface free of a natural oxide film, deposits, and the like was exposed.

Next, a process of forming an oxide film on a clean surface cleaved in an ultra-high vacuum atmosphere will be described. FIG. 5 is a process chart showing an oxide film forming procedure. FIG. 5 (a)
FIG. 4 is a view showing a state of the laser bar 32 before an oxide film is formed. On the laser bar 32, laser stripes 4 indicating light emitting portions of the laser elements are arranged. This laser bar 3
Reference numeral 2 denotes a laser bar 43 that has been cleaved in a previous step in the processing chamber 21, and a clean surface is exposed on one end face of the laser bar 32. By introducing high-purity oxygen into this processing chamber and oxidizing the cleaved end face 2, an oxide film 3 is formed.
To form

When oxidizing the cleaved end face 2, light may be applied to accelerate the oxidation. Specifically, after introducing high-purity oxygen into the processing chamber 21, as shown in FIG. 5B, a halogen lamp 51 is installed at a position facing the cleavage plane of the laser bar 32, and then the halogen lamp light is emitted. Irradiation is performed to form an oxide film having a controlled composition on the cleaved end face.

Further, for the same purpose, the temperature of the sample holder 31 may be increased, and the oxidation may be promoted by heat. When the cleavage end face 2 is oxidized, the temperature of the sample holder 31 may be increased within a range where the semiconductor laser element is not deteriorated, and the formation of an oxide film may be promoted. The upper limit of the heating temperature depends on the material system used.

After an oxide film is formed in a high-purity oxygen atmosphere, the laser bar 32 is taken out of the apparatus into the atmosphere, a protective film is formed by controlling the reflectivity of a normal dielectric, and the laser bar is cut for each laser stripe 4. The semiconductor laser device is completed by converting it into a laser device.

Next, a second embodiment of the present invention will be described. FIG. 6 is a configuration diagram showing a second embodiment of the present invention. Referring to FIG. 6, a second embodiment of the present invention is similar to the first embodiment, except that the semiconductor laser device 1,
A cleavage end face 2 formed by cleavage in a vacuum and a gallium oxide protective film 61 formed on the cleavage end face 2 are formed. This gallium oxide protective film 61
Japan Journal of Applied Physics (Jpn. J. Appl. Phys.), 32, 5661,
According to a report by Tone et al. In 1993, the first of the present invention
Among the components of the photo-oxidized film used as the end face protective film in the embodiment, it is particularly stable and is an effective material as the end face protective film.

A manufacturing process according to the second embodiment of the present invention will be described. The cleavage end face 2 is, as in the first embodiment,
Using the apparatus shown in FIG. 2 and the sample holder shown in FIG. 3, a cleavage is performed in an ultra-high vacuum atmosphere according to the procedure shown in FIG. An exposed laser bar 32 is obtained.

Next, a step of forming a gallium oxide film on a clean surface cleaved in an ultra-high vacuum atmosphere according to a second embodiment of the present invention will be described. FIG. 7 is a process diagram showing a procedure for forming a gallium oxide film. FIG. 7A is a diagram illustrating a state of the laser bar 32 before the gallium oxide film is formed. On the laser bar 32, laser stripes 4 indicating light emitting portions of the laser elements are arranged. In the pre-cleaving step of the laser bar 32 in the processing chamber 21, the cleaved laser bar 43 is separated, and a clean surface is exposed at one end face of the laser bar 32.

Next, the sample holder 31 to which the laser bar 32 is fixed is moved from the processing chamber 21 to the exchange chamber 23 using the first magnet feedthrough 25, and further,
The second magnet feedthrough 26 is used to move from the exchange chamber 23 to the growth chamber 22. The growth chamber 22 has a gallium deposition source 71. As shown in FIG. 7B, in the growth chamber 22, a gallium molecular beam 72 is irradiated on the cleavage end face of the laser bar 32 using a gallium vapor deposition source 71, and several atomic layers of a metal layer are formed on the cleavage end face. Deposit.

Then, the sample holder 31 is transferred from the growth chamber 22 to the processing chamber 21 via the exchange chamber 23 again using the first and second magnet feedthroughs 25 and 26. Next, similarly to the first embodiment, the processing chamber 21
, High-purity oxygen is introduced. Then, in the same manner as in the first embodiment, the gallium deposition layer on the cleavage surface of the laser bar 32 is oxidized, and a gallium oxide protective film 61 is formed on the cleavage end surface. When the gallium oxide protective film 61 is formed, similarly to the first embodiment, a halogen lamp light 52 may be irradiated by a halogen lamp 51 to promote oxidation, or the temperature of the sample holder 31 may be reduced by a semiconductor laser device. May be increased in a range where does not deteriorate. The means for light irradiation is not particularly limited, and a laser beam, an ultraviolet lamp, a white light other than a halogen lamp, or the like can be used in addition to a halogen lamp.

After forming the gallium oxide protective film 61, as in the first embodiment, the laser bar 32 is taken out of the apparatus into the atmosphere, and a protective film whose reflectance is controlled by a normal dielectric is formed. A laser element is formed by cutting each stripe 4 to complete a semiconductor laser element.

In the description of the first and second embodiments of the present invention, the case where the oxide film is formed only on one of the two cleaved laser end surfaces has been described. The oxide film may be formed on the other end surface of the laser bar 32.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 8 is a schematic view showing the configuration of the first embodiment of the present invention. First, a method for manufacturing a semiconductor laser wafer for manufacturing the semiconductor laser device according to the present embodiment will be described. In this embodiment, a semiconductor laser having an oscillation wavelength of 0.98 μm and having a strained quantum well structure made of GaInAs will be described as an example.

The semiconductor laser wafer of this embodiment has a normal pressure.
It grows by the chemical vapor deposition method. First, Si-doped Ga
GaAs doped with Si on an As (001) substrate 89
Buffer layer 88 (impurity concentration: 1 × 10¹⁸c
m^-3) From 0.5 μm, Si-doped AlGaAs
Formed first cladding layer 87 (impurity concentration 1 × 10
¹⁷m ^-3) At a growth temperature of 700 ° C. and a V / III ratio of 100
Under conditions, it grows by 2 μm. Next, on top of that, the luminescent layer
Grow 86. FIG. 9 shows a layer structure of the light emitting layer 86. This
A light emitting layer 86 is formed on the first cladding layer 87 by AlG.
a first light guide layer 91 made of aAs and having a thickness of 40 nm;
A first barrier layer 92 made of GaAs and having a thickness of 20 nm;
4.5 nm thick made of Ga0.76In0.24As
20 nm thick second active layer GaAs
Barrier layer 94, Ga_0.76In_0.243. thickness of As
5 nm second active layer 95, GaAs thickness 20
nm third barrier layer 96, Al_0.2Ga_0.8Composed of As
The second light guide layer 97 having a thickness of 40 nm is sequentially grown at a growth temperature.
Growing under the conditions of 680 ° C and V / III ratio 80
Formed. Further, on the light emitting layer 86, M
g-doped Al_0.4Ga_0.6Second cladding layer made of As
85 (impurity concentration 1 × 10¹⁸cm^-3) At 1.5 μm, M
Cap layer 84 made of g-doped GaAs (impurity concentration
1 × 10¹⁹cm^-3) Under the same conditions as for the light emitting layer 86
After the growth of 0.1 μm, the growth of the laser wafer is completed.

Next, this laser wafer is taken out of the growth apparatus, and SiO 2 is deposited on the cap layer 84 shown in FIG.
₂ is deposited, using the photolithographic technique,
A current confinement layer 83 made of SiO ₂ having a stripe-shaped opening having a width of 2 μm in the [−111] direction is formed. Next, the GaAs (001) substrate 89 and the S
First and second contact electrodes 82 and 90 are formed on both surfaces of the iO ₂ stripe 83, respectively, to obtain a semiconductor laser wafer. After that, it goes straight to the laser stripe [11
The laser bar 32 is obtained by cleavage along the 0] direction so that the cavity length becomes 1200 μm.

Next, a process of cleaving the laser bar 32 in an ultra-high vacuum atmosphere and forming an oxide film on the cleaved end face will be described. The laser bar 32 has 700 μm from the end in advance.
The position m is scratched, fixed to the sample holder 31, and introduced into the processing chamber 21 under an ultra-high vacuum atmosphere. The degree of vacuum in the processing chamber is 1 × 10 ⁻¹⁰ Torr. Subsequently, the laser bar 32
After the linear introducer 41 having the cleavage plate 42 mounted thereon is brought close to the sample holder 31, the sample holder 31 is moved to cleave the laser bar 32.

Next, 99.999 purity is placed in the processing chamber 21.
After 9% oxygen gas is introduced until the pressure in the processing chamber 21 becomes 1 atm, the temperature of the sample holder 31 is raised to 100 ° C., and the output of the halogen lamp 51 disposed at a position opposite to the laser bar 32 is 138 mW. A halogen lamp light 52 of / cm ^-3 is irradiated for one hour to form an oxide film 81. Here, the heating temperature at the time of forming the oxide film 81 needs to be in a range where the semiconductor laser element does not deteriorate. In the material system of this embodiment, the temperature is preferably set to 300 ° C. or lower.

Thereafter, the laser bar 32 is taken out of the processing chamber 21, a dielectric film having a controlled reflectance is formed on both end surfaces of the laser bar 32, and the laser bar 32 is cut for each laser stripe 4 to form a laser device, thereby completing a semiconductor laser device. Let it.

Next, a second embodiment will be described. FIG.
FIG. 2 is a schematic sectional view of a layer structure of a light emitting layer of the semiconductor laser device of the present invention. The difference from the first embodiment is that a gallium oxide film 101 is used as an end face protective film. In the second embodiment, since the process of manufacturing the laser bar 32 is the same as that of the first embodiment, only the subsequent process of forming the end face protective film will be described.

The laser bar 32 cleaved in the processing chamber 21 under an ultra-high vacuum atmosphere has a degree of vacuum of 1 × 10 ⁻¹⁰ Torr.
Growth chamber 22 (vacuum degree: 1 × 10
^-10 Torr). Next, in the growth chamber 22, a molecular beam intensity of 2.3 × 1
A gallium molecular beam 72 of 0 ^-7 Torr is irradiated to form a gallium layer of about several atomic layers. Subsequently, the laser bar 32 is transferred to the processing chamber 21 again through the exchange chamber 23, and the gallium layer is oxidized. The oxidation process and conditions are the same as in the first embodiment. After oxidizing the gallium layer to form the gallium oxide layer 101, the laser bar 32 was removed from the processing chamber 21 and the reflectance was controlled at both end faces of the laser bar 32, as in the first embodiment. A dielectric film is formed and cut into laser stripes 4 to form a laser device, thereby completing a semiconductor laser device.

In the above two embodiments, GaIn
Oscillation wavelength 0.98 having a strained quantum well structure made of As
Although an example in which the present invention is applied to a semiconductor laser in the μm band has been described, the method of the present invention can also be applied to a semiconductor laser device having other wavelengths and materials. Further, the structure of the semiconductor laser device is not limited to that of the present embodiment, but can be applied to a general semiconductor laser in which the end face of the resonator is deteriorated (optical damage).

[0039]

As described above, according to the present invention,
The semiconductor laser bar is cleaved in an ultra-high vacuum atmosphere, and the cleaved surface of the formed semiconductor laser device is exposed to gallium on the surface of the semiconductor itself or the cleaved surface of the similarly formed semiconductor laser device is irradiated with high-purity oxygen. By using an oxide film formed by oxidation in an atmosphere as a surface protective film, the COD level of the semiconductor laser device can be improved. The oxide film formed by this vacuum integrated process is different from the natural oxide film usually formed in the atmosphere,
Since it does not contain impurities such as residual carbon, the density of surface states existing between the semiconductor and the end face protective film can be significantly reduced, and the COD level of the semiconductor laser device can be improved, resulting in high output and high reliability. A semiconductor laser device having the property can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic view of a semiconductor laser device of the present invention.

FIG. 2 is a diagram showing an example of an apparatus for manufacturing a semiconductor laser device of the present invention.

FIG. 3 is a schematic view of a sample holder for cleaving a sample.

FIG. 4 is a view showing a cleavage procedure in the present invention.

FIG. 5 is a view showing an oxide film forming step in the present invention.

FIG. 6 is a schematic view of a semiconductor laser device of the present invention.

FIG. 7 is a diagram showing a procedure for forming a gallium oxide film.

FIG. 8 is a schematic view of a semiconductor laser device of the present invention.

FIG. 9 is a schematic sectional view of a layer structure of a light emitting layer of the semiconductor laser device of the present invention.

FIG. 10 is a schematic view of a semiconductor laser device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser element 2 cleavage end face 3 oxide film 4 laser stripe 21 processing chamber 22 growth chamber 23 exchange chamber 24 gate valve 25 first magnet feedthrough 26 second magnet feedthrough 31 sample holder 32 laser bar 41 linear introducer 42 plate 43 cleaved laser bar 51 halogen lamp 52 halogen lamp light 61 gallium oxide protective film 71 gallium vapor deposition source 72 gallium molecular beam 81 oxide film 82 first contact electrode 83 current confinement layer 84 cap layer 85 second cladding layer 86 light emitting layer 87 first clad layer 88 buffer layer 89 substrate 90 second contact electrode 91 first light guide layer 92 first barrier layer 93 first active layer 94 second barrier layer 95 second active layer 96 Third barrier layer 97 Second light guide Layer 101 Gallium oxide film

Claims (8)

[Claims] 1. A semiconductor laser device having a protective film provided on an end face of a resonator, wherein the protective film cleaves a wafer for a semiconductor laser device in an ultra-high vacuum atmosphere, and then changes a cleavage surface of the wafer. A semiconductor laser device characterized by being an oxide film formed by being exposed to an oxygen atmosphere without being exposed to an air atmosphere. 2. A semiconductor laser device in which a protective film is provided on an end face of a resonator, wherein the protective film cleaves a semiconductor laser device wafer in an ultra-high vacuum atmosphere, and then changes a cleavage surface of the wafer. A semiconductor laser device characterized by being an oxide film formed by heating in an oxygen atmosphere without being exposed to an air atmosphere. 3. A semiconductor laser device in which a protective film is provided on an end face of a resonator, wherein the protective film cleaves a wafer for a semiconductor laser device in an ultra-high vacuum atmosphere, and then changes a cleavage surface of the wafer. A semiconductor laser device comprising an oxide film formed by irradiating light in an oxygen atmosphere without exposure to an air atmosphere. 4. The semiconductor laser device according to claim 1, wherein said oxide film is a gallium oxide film. 5. A step of cleaving a wafer for a semiconductor laser device under an ultra-high vacuum atmosphere, and placing an oxide film on a cleaved end face of the wafer by exposing the wafer to an oxygen atmosphere without exposing the wafer to an air atmosphere. Forming a semiconductor laser device. 6. A step of cleaving a wafer for a semiconductor laser device in an ultra-high vacuum atmosphere, and heating the wafer in an oxygen atmosphere without exposing the wafer to an air atmosphere, thereby forming an oxide film on the cleaved end face of the wafer. Forming a semiconductor laser device. 7. A step of cleaving a wafer for a semiconductor laser device under an ultra-high vacuum atmosphere, and oxidizing the cleaved end face of the wafer by irradiating the wafer with light in an oxygen atmosphere without exposing the wafer to an air atmosphere. Forming a film. 8. A step of cleaving a semiconductor laser device wafer in an ultra-high vacuum atmosphere, a step of irradiating gallium on a cleaved end face of the wafer, and a step of placing the wafer in an oxygen atmosphere to form a gallium oxide film. Forming a semiconductor laser device.