JPH09232668A - Surface light emitting semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting semiconductor laser of certain structure in which laser beams can be controlled in the plane of polarization from the outside without deteriorating the semiconductor laser in laser emission characteristics. SOLUTION: A surface light emitting semiconductor laser emits laser beams in a direction vertical to a substrate, in which a semiconductor laminated body is etched to the half-way point of a P-type clad layer 107 into a pillar part 114 which is square from in a top vies. The periphery of pillar part 114 is embedded with a first insulating layer 109 and a metal layer 110, furthermore, a second insulating layer 111 is formed on the surface of the metal layer 110, and a split upper electrode 112 into which a current can be independently injected is formed so as to come into contact with a contact layer 108 along the four sides of the square form.

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 capable of controlling the polarization plane of laser light from the outside.

[0002]

2. Description of the Related Art Conventionally, as a method of controlling a polarization plane of a laser beam of a surface emitting semiconductor laser, Japanese Patent Application Laid-Open No. 05-05570 is disclosed.
Japanese Patent No. 4 is disclosed.

The applicants of the present invention have also disclosed Japanese Patent Laid-Open No. 6-283818.
The publication discloses a structure capable of controlling the polarization plane of each surface-emitting type semiconductor laser.

[0004]

However, in the above-mentioned conventional method, since the structure of the surface emitting semiconductor laser has a structure capable of controlling the polarization plane in advance, the direction of the polarization plane is determined at the time of manufacturing. However, it is impossible to arbitrarily change the polarization plane direction of the same surface emitting semiconductor laser device.

Further, in Japanese Unexamined Patent Publication No. 4-242989,
Although a method of controlling the polarization plane of the surface-emitting type semiconductor laser from the outside is disclosed, at least two surface-emitting lasers must be prepared for one light-emitting portion, which limits integration. It was

Therefore, an object of the present invention is to provide a surface-emitting type semiconductor laser having a structure capable of controlling the polarization plane of laser light from the outside without deteriorating the laser emission characteristics of the surface-emitting type semiconductor laser. .

[0007]

In the surface-emitting type semiconductor laser of the present invention, an optical resonator for emitting laser light in a direction perpendicular to the substrate is formed on the substrate. The optical resonator includes a pair of reflection mirrors and a multi-layer semiconductor layer formed between the pair of reflection mirrors and including at least an active layer and a clad layer, and at least the clad of the multi-layer semiconductor layer. The upper layer side including the layer is a columnar portion formed in a columnar shape, a metal layer is embedded around the columnar portion through an insulating layer, and the end surface of the columnar portion is divided into a large number of openings having a desired opening. An upper electrode is further provided and is formed so that the cross-sectional shape of the columnar portion in the direction parallel to the substrate is a regular polygon.

By thus embedding the periphery of the columnar portion with the metal layer via the insulating layer, the boundary condition of the electric field distribution around the columnar portion can be made uniform. Therefore, the boundary condition of the electric field distribution of the laser light propagating in the columnar portion is also uniform.

As described above, when the electric field distribution around the columnar portion is uniform, if the shape of the horizontal cross section of the columnar portion is partially distorted, the boundary condition for the electric field distribution around the columnar portion is changed. However, the boundary condition is such that only an electric field in a specific direction can exist. Therefore, the electric field of the laser light propagating in the columnar portion can exist only in a specific direction, and the polarization plane is fixed.

Therefore, when the cross-sectional shape of the columnar portion is distorted in a specific direction, the plane of polarization of the surface-emitting type semiconductor laser can be controlled in the specific direction.

Further, not only by changing the cross-sectional shape of the columnar portion but also by changing the electric field distribution in the specific direction around the columnar portion, the polarization plane can be controlled for the same reason as described above.

Therefore, in the present invention, as a method of changing the cross-sectional shape of the columnar portion or changing the electric field distribution around the columnar portion, the upper electrode having desired openings at the end face of the columnar portion is divided into a large number of 1 The structure is such that current can be injected from the specific upper electrode into the two columnar portions.

The invention of claim 2 defines that the cross-sectional shape of the columnar portion in the direction parallel to the substrate is square. When the cross-sectional shape is a square, it is easy to take two directions in which the polarization planes of laser light are orthogonal to each other, and a stable polarization plane can be obtained.

According to a third aspect of the invention, a semiconductor multilayer mirror having an optical resonator formed on a substrate, a first cladding layer formed on the semiconductor multilayer mirror, and a first cladding layer formed on the first cladding layer are provided.
An active layer having a quantum well structure, a second clad layer formed on the active layer, a contact layer formed on the second clad layer, and an opening of the upper electrode on the contact layer. Including a formed dielectric multilayer mirror,
It is defined that the columnar portion is composed of the second cladding layer and the contact layer.

According to a fourth aspect of the invention, a semiconductor multilayer mirror having an optical resonator formed on a substrate, a first clad layer formed thereon, and a first clad layer formed on the first clad layer are provided.
Active layer of quantum well structure, second clad layer formed on the active layer, semiconductor multilayer mirror formed on the second clad layer, and contact layer formed on the semiconductor multilayer mirror It is defined that the columnar portion is constituted by the second cladding layer, the semiconductor multilayer film mirror, and the contact layer.

According to a fifth aspect of the invention, the substrate is Si, GaAl.
It is defined to be any of As-based, GaInP-based, ZnSSe-based, InGaN-based semiconductor substrates, or any one of silicon oxide, aluminum oxide, aluminum nitride, and silicon nitride dielectric substrates.

[0017]

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

(Embodiment 1) FIG. 1 is a sectional view schematically showing a section of a surface-emitting type semiconductor laser capable of controlling the plane of polarization in an embodiment of the present invention, and FIG. 2 is a schematic perspective view thereof.

A surface emitting semiconductor laser 1 shown in FIGS. 1 and 2.
The structure of the n-type GaAs substrate 102 will now be described.
780 nm consisting of an n-type GaAs buffer layer 103, an n-type AlAs layer and an n-type Al0.3Ga0.7As layer
40 pairs of distributed reflection type semiconductor multilayer mirrors 104, n-type Al0.5G having a reflectance of 99% or more with respect to nearby light
a0.5As clad layer 105, n-type Al0.1Ga
0.9As well layer and n-type Al0.4Ga0.6As
A multi-quantum well active layer 106 composed of a barrier layer having 20 well layers, p-type Al0.5Ga0.5A
s clad layer 107 and p-type Al0.2Ga0.8As
The contact layer 108 is sequentially stacked. Epitaxial growth by the MOVPE method was used to form this stack.

Then, p-type Al0.5Ga0.5As
The columnar portion 114 is etched up to the middle of the clad layer 107 into a square shape as seen from the top surface of the semiconductor laminate.
Is formed. When the cross section of the columnar portion 114 parallel to the substrate 102 is square, the direction of the plane of polarization of the laser light emitted from the oscillation region of the columnar portion 114 is either of two sides orthogonal to each other.

Around the periphery of the columnar portion 114, thermal CVD is performed.
Silicon oxide film such as SiO2 (S
A first insulating layer 109 made of an iOX film) and a metal layer 110 made of a metal such as a gold-zinc alloy are embedded.

The first insulating layer 109 is p-type Al0.5Ga.
0.5 As clad layer 107 and contact layer 108
The metal layer 110 is continuously formed along the surface of the first insulating layer 109 and is embedded in the periphery of the first insulating layer 109.

Further, a silicon oxide film (SiO 2) such as SiO 2 formed on the surface of the metal layer 110 by a sputtering method.
A second insulating layer 111 made of an X film), and a contact metal layer (upper electrode) 112 made of, for example, Cr and a gold-zinc alloy is formed on the second insulating layer 111 in contact with the contact layer 108. It becomes an electrode for.

The upper electrode 112 is divided into four and is formed along each side of a square, which is the cross-sectional shape of the columnar portion 114, and the central portion of the square is exposed without being covered by the upper electrode 112. The first layer, for example, a SiOX layer such as SiO 2 and the second layer, for example, a TaOX layer such as Ta 2 O 5 are alternately arranged in an area that sufficiently covers the exposed surface of this contact layer 108 (hereinafter, this portion is referred to as “opening 115”). And 8 pairs of dielectric multilayer mirrors 113 having a reflectance of 98.5% or more with respect to light near the wavelength of 780 nm are formed.

A lower electrode 101 made of a gold-germanium alloy is formed below the substrate 102.

In FIG. 2, the columnar portion 114 shows one surface-emitting type semiconductor laser for simplification.
Even if there are a plurality of columnar portions in the substrate surface, the form of the present invention is not impaired.

Next, a method for controlling the plane of polarization of laser light in the surface emitting semiconductor laser shown in this embodiment will be described.

FIG. 3 is a schematic view of the surface-emitting type semiconductor laser of this embodiment as viewed from the side where the laser is emitted. Here, the dielectric multilayer mirror 113 is not shown for simplification. The upper electrode 112 is formed along each side of the square contact layer 108. The two upper electrodes 112 facing each other 2
The upper electrodes 112A and 11 are each divided into two pairs,
Divide into 2B.

In order to drive the surface emitting semiconductor laser, a current is injected from the upper electrode 112 and the current is applied to the active layer 1.
Then, the current is converted into light, the light is amplified in the optical resonator, and finally the laser light is emitted from the opening 115.

Here, in the surface-emitting type semiconductor laser of this embodiment, when the laser is driven using only the upper electrode 112A, the current is diffused from the two sides of the square in contact with the upper electrode 112A toward the central portion of the square. While being guided to the active layer 106, laser oscillation occurs. The other upper electrode 1
When the laser is driven using only 12B, the upper electrode 1
Similarly, the current spreads from two sides orthogonal to the two sides of the square 12A in contact with the active layer 1 while spreading toward the center of the square.
It is guided to 06, and laser oscillation occurs.

At this time, since the cross-sectional shape of the columnar portion 114 is square and the upper electrodes 112A and 112B are symmetrically formed, the surface emitting type driven by using only the upper electrodes 112A and 112B. Device characteristics of semiconductor laser (oscillation threshold current, current-light conversion efficiency, etc.)
There is no difference.

However, when only the upper electrode 112A is used and when only the upper electrode 112B is used, the influence on the electric field distribution in the vicinity of the interface between the inside of the columnar portion 114, which is a part of the optical resonator, and the surroundings is affected. Different ways. When the surface-emitting type semiconductor laser is not driven, the electric field distribution around the columnar portion 114 is the same for each side of the square due to the metal layer 110 formed around the columnar portion 114. At this time, the polarization plane of the laser light that can exist inside the columnar portion 114 is either one of the two sides of the square that are orthogonal to each other and cannot be determined.

When a current is injected into the surface-emitting type semiconductor laser using the upper electrode 112A, the electric field distribution near the interface of the columnar section 114 changes, and inside the columnar section 114, the side of the square in contact with the upper electrode 112A is changed. Is likely to have an electric field in the orthogonal direction. Therefore, the polarization plane of the light propagating in the columnar portion 114 is also orthogonal to the side of the square in contact with the upper electrode 112A, and the polarization plane of the emitted laser light is also in the direction in which the electric field easily exists. .

Similarly, when a current is injected into the surface-emitting type semiconductor laser using the upper electrode 112B, the plane of polarization of the laser light emitted is the square side where the upper electrode 112B is in contact with the side where the upper electrode 112A is in contact. Since they are orthogonal to each other, the directions are orthogonal to the direction of the polarization plane of the laser light using the upper electrode 112A.

Therefore, in the surface-emitting type semiconductor laser of this embodiment, the direction of the plane of polarization of the emitted laser light can be controlled by selecting the upper electrode 112A or 112B and passing an electric current. Further, when the cross-sectional shape of the columnar portion 114 is square, the laser light has orthogonal polarization planes, and thus stable laser oscillation is achieved.

(Embodiment 2) FIG. 4 is a sectional view schematically showing a section of a surface emitting semiconductor laser capable of controlling the polarization plane in the second embodiment of the present invention. The present embodiment differs from the structure of the first embodiment in that both the pair of reflection mirrors forming the optical resonator are formed of semiconductor multilayer film mirrors.

The structure of the surface-emitting type semiconductor laser 200 shown in FIG. 4 will be described. On the n-type GaAs substrate 202,
The n-type GaAs buffer layer 203, the n-type AlAs layer and the n-type Al0.5Ga0.5As layer 60 pairs of distributed reflection type semiconductor multilayer mirrors 204 having a reflectance of 99% or more for light near 650 nm. Al0.7Ga0.
3As clad layer 205, n-type Ga0.5In0.5
P-well layer and n-type (Al0.5Ga0.5) 0.5I
A multiple quantum well active layer 206 composed of n0.5P barrier layers and five well layers, p-type Al0.7Ga
A 0.3 As clad layer 207, a p-type AlAs layer and a p-type Al0.5Ga0.5As layer, and 50 pairs of distributed reflection type semiconductor multilayer film mirrors 208 having a reflectance of 98.5% or more for light near 650 nm, and p-type Al0.3G
The a0.7As contact layer 209 is sequentially stacked. Epitaxial growth by the MBE method was used to form this stack.

Then, the columnar portion 214 is formed up to the middle of the p-type cladding layer 207 by etching into a square shape as viewed from the top surface of the semiconductor laminate.

Around the columnar portion 214, thermal CVD is performed.
A first insulating layer 210 made of a silicon nitride film (SiNX film) formed by the method and a metal film 211 made of a metal such as aluminum are embedded.

The first insulating layer 210 is the p-type cladding layer 20.
7. The metal layer 211 is formed continuously along the surfaces of the p-type semiconductor multilayer film mirror 208 and the contact layer 209.
Are formed so as to fill the periphery of the first insulating layer 210.

Further, a second insulating layer 212 made of a silicon nitride film (SiNX film) formed by a sputtering method is formed on the surface of the metal layer 211, and a contact metal layer (upper part) made of, for example, Cr and gold is formed thereon. An electrode) 213 is formed in contact with the contact layer 209 and serves as an electrode for current injection.

The upper electrode 213 is divided into four parts, each of which is formed along each side of the square which is the cross-sectional shape of the columnar part 214, and the central portion of the square is exposed without being covered by the upper electrode 213 ( After that, this portion is referred to as “opening 21
5 ”).

A lower electrode 201 made of a gold-germanium alloy is formed below the substrate 202.

In FIG. 4, the columnar portion 214 shows one surface-emitting type semiconductor laser for simplification.
Similar to the first embodiment, even if there are a plurality of columnar portions in the substrate surface, the form of the present invention is not impaired.

Next, a method for controlling the plane of polarization of laser light in the surface-emitting type semiconductor laser shown in this embodiment will be described.

FIG. 5 is a schematic view of the surface-emitting type semiconductor laser of this embodiment as viewed from the side from which the laser is emitted. The upper electrode 213 is formed along each side of the square contact layer 209. These four upper electrodes 213 are divided into two sets that oppose each other and are divided into two upper electrodes 213A and 213B, respectively.

Also in this embodiment, since the metal layer 211 is formed around the periphery of the columnar portion 214, as in the structure of the surface emitting semiconductor laser shown in the first embodiment, the periphery of the columnar portion 214 is formed. The electric field distribution of is the same for each side of the square.

However, in this embodiment, as compared with the structure shown in the first embodiment, the cladding layer 207,
Since the semiconductor multilayer mirror 208 and the contact layer 209 are laminated, the distance from the active layer 206 to the upper electrode 213 is long. Therefore, in the structure of this embodiment, the method of controlling the polarization plane by influencing the electric field distribution around the columnar portion 214 shown in Embodiment 1 is the upper electrode 213.
Since it is difficult for the electric field given by to be transmitted around the columnar portion directly above the active layer 206, it is difficult to control the polarization plane.

Therefore, in this embodiment, the material of the upper electrode 213 is selected to increase the contact resistance with the contact layer 209 (hereinafter referred to as contact resistance). When a current is passed through the upper electrode 213 by increasing the contact resistance, the temperature of the portion where the upper electrode 213 and the contact layer 209 are in contact with each other slightly rises.

Therefore, first, when the laser is driven using only the upper electrode 213A, the temperature of the portion in contact with the upper electrode 213A slightly rises as compared with the portion in contact with the upper electrode 213B. Then, due to the temperature difference, the columnar portion 214
Is slightly distorted, and the square shape becomes a rectangular shape in which the side in contact with the upper electrode 213B slightly extends.

Then, the boundary condition of the electric field distribution around the columnar portion 214 changes, and the electric field in the direction orthogonal to the side of the square with which the upper electrode 213B is in contact tends to exist inside the columnar portion 214. Therefore, the polarization plane of the light propagating inside the columnar portion 214 is also orthogonal to the side of the square in contact with the upper electrode 213B, and the polarization plane of the emitted laser light is also in the direction in which the electric field is likely to exist. .

Similarly, when a current is injected into the surface-emitting type semiconductor laser using the upper electrode 213B, the plane of polarization of the laser light emitted is the square side where the upper electrode 213B is in contact with the side where the upper electrode 213A is in contact. Since they are orthogonal to each other, they are orthogonal to the direction of the polarization plane of the laser light using the upper electrode 213A.

Therefore, in the surface-emitting type semiconductor laser of this embodiment, the direction of the plane of polarization of the emitted laser light can be controlled by selecting the upper electrode 213A or 213B and passing an electric current. Further, in the structure of the present invention, since the electrodes of one surface-emitting type semiconductor laser device are divided, the integration of the devices is not affected.

Further, since the cross-sectional shape of the columnar portion 214 is square and the upper electrodes 213A and 213B are symmetrically formed, only the upper electrodes 213A and 2 are formed.
There is no difference in device characteristics (oscillation threshold current, current-light conversion efficiency, etc.) of the surface-emitting type semiconductor laser driven by using only 13B.

As described above in detail, when the surface-emitting type semiconductor laser of the present invention is used, it is possible to control the polarization plane of laser light from the outside without impairing the laser emission characteristics of the surface-emitting type semiconductor laser. Become.

Further, the present invention is not limited to the above embodiment, but various modifications can be made within the scope of the gist of the present invention.

If the cross-sectional shape of the columnar portion constituting the optical resonator is changed from square to regular hexagonal and the upper electrode is divided into 6 in contact with each side, the plane of polarization can be controlled in three directions. .

The substrate is made of Si or GaA depending on the material of the semiconductor layer which determines the oscillation wavelength of the surface emitting semiconductor laser.
Any of 1As-based, GaInP-based, ZnSSe-based, and InGaN-based semiconductor substrates, or silicon oxide, aluminum oxide, aluminum nitride, or silicon nitride dielectric substrates may be used. It is possible to carry out by replacing each.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a cross section of a surface-emitting type semiconductor laser capable of controlling a polarization plane according to an embodiment of the present invention. FIG. 2 is a schematic perspective view thereof.

FIG. 2 is a schematic perspective view of the surface-emitting type semiconductor laser shown in FIG.

FIG. 3 is a schematic view of the surface emitting semiconductor laser shown in FIG. 1 as viewed from a side from which the laser emits.

FIG. 4 is a cross-sectional view schematically showing a cross section of a surface-emitting type semiconductor laser capable of controlling a polarization plane according to another embodiment of the present invention.

FIG. 5 is a schematic view of the surface-emitting type semiconductor laser shown in FIG. 4 when viewed from the side from which the laser emits.

[Explanation of symbols]

101, 201 lower electrode 102, 202 n-type GaAs substrate 103, 203 n-type GaAs buffer layer 104, 204, 208 distributed reflection semiconductor multilayer film mirror 105 n-type Al0.5Ga0.5As clad layer 106, 206 multiple quantum well active layer 107 p-type Al0.5Ga0.5As clad layer 108 p-type Al0.2Ga0.8As contact layer 109,210 first insulating layer 110,211 metal layer 111,212 second insulating layer 112,112A, 112B, 213,213A, 21
3B Upper electrode 113 Dielectric multilayer mirror 114,214 Columnar part 115,215 Opening 205 n-type Al0.7Ga0.3As clad layer 207 p-type Al0.7Ga0.3As clad layer 209 p-type Al0.3Ga0.7As contact layer

Claims (5)

[Claims] 1. A surface-emitting type semiconductor laser in which an optical resonator for emitting laser light in a direction perpendicular to the substrate is formed on a substrate, wherein the optical resonator includes a pair of reflection mirrors and a pair of reflection mirrors. A multi-layer semiconductor layer formed between the mirrors and including at least an active layer and a clad layer, and an upper layer side of the multi-layer semiconductor layer including at least the clad layer is a columnar portion formed in a columnar shape, A metal layer is embedded around the columnar portion with an insulating layer interposed therebetween, and a plurality of upper electrodes having desired openings are further provided on the end face of the columnar portion, and the upper electrode is parallel to the substrate of the columnar portion. A surface-emitting type semiconductor laser having a regular polygonal cross section in the direction. 2. The surface emitting semiconductor laser according to claim 1, wherein the cross-sectional shape of the columnar portion in the direction parallel to the substrate is square. 3. The mirror according to claim 1, wherein, of the pair of reflection mirrors, the mirror formed on the substrate is a semiconductor multilayer film mirror, and the optical resonator is the semiconductor multilayer film mirror. A first clad layer formed thereon, an active layer having a quantum well structure formed on the first clad layer, a second clad layer formed on the active layer, and a second clad layer A contact layer formed on the clad layer, and a dielectric multilayer mirror formed on the contact layer so as to cover the opening of the upper electrode, wherein the columnar portion is formed by the second clad layer and the contact layer. A surface-emitting type semiconductor laser having a structure. 4. The semiconductor multilayer film mirror according to claim 1, wherein the pair of reflecting mirrors are semiconductor multilayer film mirrors, and the optical resonator is a semiconductor multilayer film mirror formed on the substrate, and a semiconductor multilayer film mirror formed on the semiconductor multilayer film mirror. The formed first clad layer, the active layer having a quantum well structure formed on the first clad layer, the second clad layer formed on the active layer, and the second clad layer formed on the second clad layer. Semiconductor multilayer film mirror,
A surface-emitting type semiconductor laser including a contact layer formed on the semiconductor multilayer film mirror, wherein the columnar portion is constituted by the second cladding layer, the semiconductor multilayer film mirror and the contact layer. 5. The substrate according to claim 1, wherein the substrate is Si, GaAlAs system, GaInP system, Zn.
1. A surface emitting semiconductor laser, which is one of an SSe-based semiconductor substrate and an InGaN-based semiconductor substrate or a silicon oxide, aluminum oxide, aluminum nitride, or silicon nitride dielectric substrate.