JPH11307863A - Surface light-emitting semiconductor laser element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection mirror which is manufactured with no dispersion in reflectivity with a reflection mirror of high reflectivity. SOLUTION: The element comprises a GaAs substrate 101, a first reflection mirror 102 comprising a multi-layer film of GaAs/AlAs provided on the GaAs substrate 101, laminating structures 103, 104, 105, and 106 constituting a light- emitting part formed on the first reflection mirror 102, and a second reflection mirror 115 formed on the laminating structures 103-106. The second reflection mirror 115 comprises a multi-layer film having a pair of a GaAs film 111 and an air layer 110 comprising an A10 supporting layer 109 along both side edges.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting semiconductor laser device and a method of manufacturing the same, and more particularly, to a surface emitting semiconductor laser having a reflector structure which is easy to manufacture and has no variation in dimensions and reflectivity. The present invention relates to an element and a method for manufacturing the element.

[0002]

2. Description of the Related Art A vertical cavity surface emitting semiconductor laser emits light in a direction perpendicular to a semiconductor substrate and is capable of two-dimensional parallel integration, such as parallel optical information processing and optical interconnection. Is attracting attention as a semiconductor laser device aimed at application to a new field of optical electronics. 2. Description of the Related Art A surface emitting semiconductor laser device (hereinafter, simply referred to as a surface emitting laser device) is a semiconductor laser device having a structure in which an active region and a reflecting mirror are provided on a semiconductor substrate and a laser beam is emitted from the substrate side. , Generally a reflectivity of 99
It is said that a reflector having a high reflectance of at least% is required.

[0003] A method of forming a reflector having a high reflectance has been actively studied in the past, and for example, a method of forming a reflector with a multilayer film as described below has been proposed. First
Is a method in which a reflecting mirror is constituted by a multilayer film composed of two types of semiconductor layers having mutually different refractive indexes. For example, a GaAs layer having a refractive index n of 3.5 and a refractive index n of 3
A high-reflectance mirror is constituted by a multilayer film formed by laminating the above-mentioned AlAs layer. This semiconductor multilayer film-type reflecting mirror has an advantage that since the respective semiconductor layers of the multilayer film constituting the reflecting mirror can be formed by the epitaxial growth method, the multilayer film can be formed simultaneously when the active region of the surface emitting laser element is formed. However, since the difference in the refractive index between the two different layers of the semiconductor material constituting each multilayer film is small, at least 20 pairs or more layers are required to obtain a reflectance of 99% or more.
The band of high reflectance is as narrow as about 80 nm.

On the other hand, a second method is to use two different dielectric materials having a large difference in the refractive index, for example, a Si film having a refractive index n of 3.2 and a refractive index n. n
When using a multilayer film in which 1.5 is a pair of a SiO ₂ film,
A reflector having a reflectivity of 99% or more can be formed by about 6 pairs, and its bandwidth is considerably wide, about 600 nm. However, the dielectric has poor heat conduction and cannot be epitaxially grown, and thus has problems such as difficulty in forming and processing a multilayer film.

[0005] In contrast to these methods, in a third method,
As shown in FIG. 4, first, an Al _x Ga _{1 -x} As (x <0.3)) film and an Al film are formed on a GaAs substrate by MBE.
_{y Ga 1-y As (y} > 0.6) to form a multilayer film of a film. Next, the Al _y Ga _1-x As (y> 0.6) film is removed by a selective etching method to form an air layer, and the Al _x Ga _1-x As (x <0.3) film and the air layer are formed. The method of forming a multilayer reflector consisting of, for example, S.-T.H
oet al., Appl. Phys. Lett., Vol. 57 pp. 1387-1389,
Proposed by 1990.

According to this method, the refractive index of air is 1 while the refractive index of a semiconductor is about 3, so that 9
A reflector having a high reflectivity of 0.6%, 29.2% for 9 pairs, and 99.9% for 3 pairs can be obtained, and has a very wide bandwidth of about 600 nm. A multilayer film can be formed by epitaxial growth. There are advantages. In addition, Al _x Ga _1-x As (x
<0.3)) film and _{Al y Ga 1-y As (} y> 0.6)
Instead of a film, a multilayer film of a GaAs film and an AlAs film is formed, and the AlAs film is selectively removed to form a GaAs film.
A multilayer film of an s film and an air layer may be formed.

[0007]

However, the above-mentioned third method
In the method of ( ₁₎ , a GaAs film or Al _x Ga _{1 -x} As (x
<0.3)) and the first layer of film, when forming a multilayer film of an air layer, as shown in FIG. 1, by selective etching, AlAs film or _{Al y Ga 1-y As (} y > 0.
6) Since the film is selectively etched in the lateral direction parallel to the film, it is technically difficult to control the etching, and a GaAs film or Al _x G as a support necessary for forming an air layer is used.
There has been a problem that the etching is excessively performed up to the a _1-x As (x <0.3) film, or conversely, a predetermined air layer cannot be formed due to insufficient etching. Therefore, it is difficult to form a multilayer film composed of a pair having a small thickness, the reproducibility of etching is poor, and the thickness of the air layer constituting the multilayer film varies, resulting in a variation in reflectance. It was a winning mirror.

As described above, the conventional method of forming a reflecting mirror does not always achieve satisfactory results. Accordingly, an object of the present invention is to provide a surface emitting laser device having a reflecting mirror structure which can be manufactured without variation in reflectance and has a high reflectance, and a method of manufacturing the same.

[0009]

In order to achieve the above object, a surface emitting semiconductor laser device according to the present invention comprises a GaAs laser.
A substrate and a GaAs / AlA provided on the GaAs substrate
s, a first reflecting mirror comprising a multilayer film, a laminated structure forming a light emitting portion formed on the first reflecting mirror, and a second reflecting mirror formed on the laminated structure. In the semiconductor laser device, the second reflecting mirror is constituted by a multilayer film having a pair of a GaAs film and an air layer defined by AlO layers provided along both side edges. And

Generally, the width of the AlO layer may be about 10 μm. In the surface emitting semiconductor laser device according to the present invention,
Instead of the GaAs film, Al _x Ga _{1 -x} As (x <0.
3) It may be composed of a multilayer film in which a film and an air layer having an AlO support layer along both side edges are paired.

In the method of manufacturing a surface emitting semiconductor laser device according to the present invention, a multi-layer film comprising a pair of a GaAs film and an AlAs film when forming a second reflecting mirror on a laminated structure constituting a light emitting portion. Forming a multi-layered film into a stripe mesa, and oxidizing a side edge of the AlAs film of the multi-layered mesa film to convert it to AlO.
The method includes a step of forming an O layer and a step of etching and removing the remaining AlAs film to form an air layer partitioned by AlO layers provided along both side edges.

In the step of forming an AlO layer, a method of oxidizing a side edge of an AlAs film of a stripe-mesa multilayer film is as follows.
There is no particular limitation, and oxidation is performed by, for example, a steam oxidation method.
In the step of forming the air layer, preferably, the remaining Al
In the etching for etching the As film, GaAs is used.
Wet etching is performed using an etchant having a large etching selectivity between Al and AlO, for example, an HF-based etchant such as a 10% aqueous HF solution.

Further, Al _x Ga _{1 -x} As (x <0.3)
Forming a multilayer film including a pair of a film and an AlAs film, and forming a multilayer mirror reflector structure including a pair of a GaAs film and an air layer having an AlO support layer along both side edges. May be. Further, a step of forming a multilayer film having a pair of a GaAs film and an Al _y Ga _1-y As (y> 0.6) film instead of the AlAs film, and replacing the GaAs film, the AlAs film, and the multilayer film with each other. And an Al _x Ga _{1 -x} As (x <0.3) film and Al
_y Ga _1-y As (y> 0.6) film and a step of forming a multilayer film as a pair, wherein Al _y Ga _1-y As (y> 0.
6) The air layer may be formed by oxidizing the film and etching the remaining portion.

In the present invention, GaAs or Al _x Ga _{1 -x}
As (x <0.3) and the AlO, AlAs or Al _y
Utilizing a difference in etching rate between Ga _1-y As (y> 0.6) and selectively using AlAs or Al _y Ga
_1-y As (y> 0.6) is removed to leave AlO layers on both side edges. Thereby, the GaAs film or Al
_x Ga _1-x As (x <0.3)) film and air layer (gap) partitioned by AlO layers provided along both side edges
Thus, it is possible to form a structurally strong and high-reflectance reflecting mirror composed of a multilayer film of the above with no variations in dimensions and reflectivity.

[0015]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 This embodiment is an example of an embodiment of a surface emitting semiconductor laser device (hereinafter simply referred to as a surface emitting laser device) according to the present invention, and FIG. FIG. 2 is a partially cutaway perspective view showing a configuration of a laser element. As shown in FIG. 1, the surface emitting laser element 10 of this embodiment includes a GaAs substrate 101 and a GaAs substrate 101 provided on the GaAs substrate 101.
a substrate-side reflecting mirror 102 comprising a multilayer film of s / AlAs;
The light emitting device includes a laminated structure forming a light emitting unit formed on the substrate-side reflecting mirror 102, a reflecting mirror 115 formed on the laminated structure, and electrodes 112 and 113. The light-emitting portion has a laminated structure including a lower cladding layer 103, an active layer 104, an upper cladding layer 105, an AlAs layer 107, and an AlAs layer 10.
7, a current confinement layer 106 made of an AlAs oxide layer and a cap layer 108 are embedded.

When the oscillation wavelength is λ, the reflecting mirror 115
A GaAs film 111 having a thickness of λ / (4n _GaAs ) and an air layer 11 having a thickness of λ / 4 having AlO support layers 109 on both side edges.
0 and at least three pairs of multilayer films. For example, when the oscillation wavelength λ is 980 nm, the refractive index n of GaAs
_{Since GaAs} = 3.5, the thickness of the _GaAs film 111 is 7
The thickness of the air layer 110 is 245 nm. The reflectance of the reflecting mirror 115 depends on the GaAs film 111 and the air layer 110.
Considering a multi-layer film having a pair of
%, 2 pairs, 99.2%, and 3 pairs, 99.9%. Further, since the refractive index difference Δn between the GaAs film and the air layer is as large as Δn = 2.5, the reflecting mirror 115 is a three-layer reflecting mirror having a wide band of about 600 nm. On the other hand, the substrate-side reflecting mirror 102 is composed of 20 to 30 pairs of GaAs / AlAs
To form a reflecting mirror having a reflectance of 99% or more.
In the surface emitting laser device 10, a current is injected from the electrode 113 formed around the reflecting mirror 115, and flows only to the active region immediately below the reflecting mirror by the current confinement layer 106, for example.

Embodiment of Manufacturing Method of Surface-Emitting Laser Device Next, a method of manufacturing the surface-emitting laser device 10 of the present embodiment will be described with reference to FIGS. FIGS. 2A to 2C and FIGS. 3D and 3E are cross-sectional views showing the layer structure in each step when manufacturing the surface emitting laser element 10 of the present embodiment. (1) First, as shown in FIG. 2A, a GaAs substrate 1
01, a substrate-side reflecting mirror 102 composed of a multilayer film of GaAs / AlAs, a lower cladding layer 103, an active layer 104,
A stacked structure of a surface emitting laser including an upper cladding layer 105, an AlAs layer 107, a current confinement layer 106 for embedding the AlAs layer 107, and a cap layer 108 is formed.
In FIG. 2A, the current confinement layer 106 is not shown. Next, the GaAs film 111 is formed on the laminated structure.
Then, a reflecting mirror structure of at least three pairs of multilayer films 115 each including one pair of AlAs films 114 is formed by an epitaxial growth method.

(2) Next, as shown in FIG.
A stripe mask (not shown) is formed on the multilayer film 115, and the multilayer film reflecting mirror structure is processed into a stripe mesa shape having a width of, for example, 30 nm by a dry etching method or a wet etching method. (3) Next, as shown in FIG. 2 (c), the side edge of the AlAs film 114 of the striped mesa-like multilayer film is oxidized to a depth of about 10 μm to be converted to AlO by a steam oxidation method.
An AlO support layer 109 is formed. (4) Subsequently, a mask having a length of about 30 μm is formed on the stripe-shaped mesa-shaped multilayer film 115 and is etched by a dry etching method to make the multilayer-film reflective mirror structure into a square pillar-shaped mesa of about 30 μm square. Then, an etching solution having a large etching selectivity between GaAs and AlO, for example, HF1
With a HF-based etchant such as a 0% aqueous solution, only the remaining AlAs is removed by etching to form a void layer, that is, an air layer 110, as shown in FIG. As a result, the GaAs film 111 and the AlO
The reflecting mirror 115 having a multilayer structure with the air layer 110 having the support layer 109 can be formed.

(5) Next, as shown in FIG.
By forming the current confinement structure, for example, the AlAs oxide layer 106 and the electrodes 112 and 113, the surface emitting laser device 10 shown in FIG. 1 can be obtained.

According to this embodiment, GaAs and Al
The etching selectivity between O and AlAs is large, for example, by using an HF-based etchant such as a 10% aqueous HF solution.
Only the remaining AlAs film is removed by etching,
Since the air gap layer, that is, the air layer 110, is formed, the reproducibility of etching is high, there is little variation among products, and the product yield can be improved.

Embodiment 2 This embodiment is a modification of the embodiment 1, and the surface emitting laser device of the embodiment 2 is different from the surface emitting laser device 1 of the first embodiment.
0 GaAs film 111, instead of Al _x Ga _{1 -x} As
(X <0.3) film and AlO support layer 10 along both side edges
The second reflecting mirror 115 is constituted by a multilayer film including a pair of the air layer 110 having the first and the second reflecting mirrors 9. At that time, in the above-mentioned step (1), Al _x Ga _{1 -x} is used instead of the GaAs film 111.
A multilayer film including a pair of an As (x <0.3) film and an AlAs film 114 is formed.

Embodiment 3 This embodiment is a modification of the surface emitting laser device 10 of Embodiment 1.
Although this example has the same configuration as that of Example 1, the manufacturing method is different. In this example, in the above-mentioned step (1), the AlAs film 11 is formed.
GaAs film 111 and Al _y Ga _1-y As
(Y> 0.6), a multilayer film is formed as a pair, and then in step (3), the Al _y Ga _1-y As (y> 0.6) film is oxidized to form an AlO support layer 109. Is formed, and the remaining Al _y Ga _{1 -y} As (y> 0.6) film is removed by etching in the step (4).

Embodiment 4 This embodiment is an example having the same structure as the surface emitting laser element of Embodiment 2 but a different manufacturing method. In this example, Al _x Ga _{1 -x} is used instead of the GaAs film 111 and the AlAs film 114 in the step (1).
As (x <0.3) film and Al _y Ga _1-y As (y> 0.
6) forming a multilayer film having a pair with the film, and then oxidizing the Al _y Ga _1-y As (y> 0.6) film in the step (3) to form the AlO support layer 109; A remaining in step 4)
_{l y Ga 1-y As (} y> 0.6) film is removed by etching.

The surface emitting laser elements of Embodiments 2 to 3 and the method of fabricating the same also exhibit the same effects as those of Embodiment 1, and have a high reflectivity with a very small logarithm of 2 to 3 pairs. A mirror can be formed. Moreover, similarly to the first embodiment, the AlAs film or the Al _y Ga _1-y As (y
> 0.6) Reproducibility of film etching is high, there is little variation in products, and product yield can be improved.

[0025]

According to the present invention, it is possible to form a pair of a GaAs film and an air layer having an AlO layer along both side edges by forming a reflecting mirror opposite to the substrate. A reflector structure having a high reflectance with a small number of logarithmic multilayer films can be manufactured without causing a variation in the reflectance. The surface emitting laser device according to the present invention is most suitable as a light source in the field of optical communication and optical interconnection.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing a layer structure of a surface emitting laser element according to a first embodiment.

FIGS. 2A to 2C are cross-sectional views illustrating a layer structure in each step when manufacturing the surface emitting laser element of the first embodiment.

FIGS. 3D and 3E are cross-sectional views showing a layer structure in each step when manufacturing the surface emitting laser element 10 of the present embodiment.

FIG. 4 is a schematic cross-sectional view of a reflecting mirror structure for explaining the configuration of a conventional reflecting mirror and its problems.

[Explanation of symbols]

10 Surface-Emitting Laser Device of Embodiment 1 101 GaAs Substrate 102 GaAs / AlAs Multilayered Film-Side Reflector 103 Lower Cladding Layer 104 Active Layer 105 Upper Cladding Layer 106 Current Confinement Layer 107 AlAs Layer 108 Cap Layer 109 AlO support layer 110 air layer 111 GaAs layer 112, 113 electrode 114 AlAs layer 115 second reflecting mirror

Claims (6)

[Claims] 1. A GaAs substrate, a first reflecting mirror made of a GaAs / AlAs multilayer film provided on the GaAs substrate, and a light-emitting portion formed on the first reflecting mirror. A surface emitting semiconductor laser device having a structure and a second reflector formed on the laminated structure, wherein the second reflector is formed by a GaAs film and an AlO layer provided along both side edges. A surface emitting semiconductor laser device comprising a multilayer film having a pair of partitioned air layers. 2. The method according to claim 1, wherein the second reflecting mirror is replaced with a GaAs film.
2. A multi-layer film comprising a pair of an Al _x Ga _{1 -x} As (x <0.3) film and an air layer having an AlO support layer along both side edges. 4. The surface emitting semiconductor laser device according to item 1. 3. The method for manufacturing a surface emitting semiconductor laser device according to claim 1, wherein a GaAs film and an AlAs film are formed when forming the second reflecting mirror on the laminated structure forming the light emitting portion. Forming a multi-layered film, a step of processing the multi-layered film into a striped mesa, oxidizing a side edge of the AlAs film of the striped mesa-shaped multi-layered film to convert it to AlO, and forming an AlO layer. Forming an air layer separated by AlO layers provided along both side edges by etching the remaining AlAs film and removing the remaining AlAs film by etching. Production method. 4. An Al _x Ga _{1 -x} A film instead of a GaAs film.
4. The method for manufacturing a surface emitting semiconductor laser device according to claim 3, further comprising the step of forming a multilayer film having a pair of an s (x <0.3) film and an AlAs film. 5. A GaAs film and an Al film instead of the AlAs film.
_{y Ga 1-y As (y} > 0.6) forming a multilayer film to the film pair, the stripe-shaped mesa-shaped multi-layer _{Al y Ga 1-y As (} y>
0.6) Oxidize the side edges of the film to convert it to AlO,
Forming a layer, and etching away the remaining Al _y Ga _1-y As (y> 0.6) film to form an air layer defined by AlO layers provided along both side edges. The method according to claim 3, further comprising the steps of: 6. An Al _x Ga _{1 -x} As (x <0.3) film and an Al _y Ga film instead of the GaAs film, the AlAs film and the multilayer film.
A step of forming a multilayer film in which a pair of a _1-y As (y> 0.6) film is formed, and Al _y Ga _1-y As (y>) of a stripe-mesa multilayer film.
0.6) Oxidize the side edges of the film to convert it to AlO,
Forming a layer, and etching away the remaining Al _y Ga _1-y As (y> 0.6) film to form an air layer defined by AlO layers provided along both side edges. The method according to claim 3, further comprising the steps of: