JP2000114657A - Surface light emitting type semiconductor laser, and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light emitting type semiconductor laser produced accurately with good repeatability, along with prompt rising response of laser light beam, and provide its manufacturing method. SOLUTION: A dielectric current constriction layer 10 with an opening 11 is formed on a p-type GaN upper spacer layer 6. By using a selective growth method, a GaN single-crystal thin film is selectively grown on the current constriction layer 10, and in addition, a material structure necessary for the surface light emitting laser is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-emitting type semiconductor laser and a method for manufacturing the same, and more particularly, to a surface-emitting semiconductor laser which has a fast rising response of laser light emission and which can be manufactured with high accuracy and good reproducibility. The present invention relates to a light emitting semiconductor laser and a method for manufacturing a surface emitting semiconductor laser.

[0002]

2. Description of the Related Art A surface-emitting type semiconductor laser comprises an active layer made of a laser medium and a pair of high-reflectivity multilayer reflective films sandwiching the active layer, and a resonator is formed by the pair of multilayer reflective films. Thereby, laser oscillation is realized. In the surface-emitting type semiconductor laser, a current confinement layer for efficiently injecting a current into a necessary portion of the active layer is further provided. This current confinement layer is an important component that affects the emission characteristics of the laser because it affects the state of current injection into the active layer.

Conventionally, as a method of forming a current confinement layer,
A proton implantation system in which protons are implanted from the outside and the electric conductivity of the implanted region is reduced to restrict the region where current flows, and a partially insulating aluminum oxide by oxidizing aluminum arsenic in a steam atmosphere There is known a selective oxidation method in which a layer is formed and a current flowing region is limited.

However, since the surface emitting semiconductor laser of the proton injection type is formed by using a semiconductor manufacturing process, the shape accuracy and reproducibility of the current confinement layer are good, but the rising response of laser emission is slow. This is because, in realizing laser oscillation, heat is generated by the flow of current in the direction of the resonator, a thermal lens effect occurs, and a difference in the effective refractive index between the current passage region and the proton injection region occurs. This is due to the formation of the optical waveguide structure.

On the other hand, in the surface-emitting type semiconductor laser of the selective oxidation method, the optical waveguide structure is steadily constituted by the aluminum oxide of the current confinement layer. When performing selective oxidation below, there is a problem in shape accuracy and reproducibility due to oxidation conditions and the influence of an oxide film on the surface existing before the oxidation treatment. In addition, since the selective oxidation method generally requires the semiconductor material to contain aluminum arsenic, applicable materials are limited, and for example, there is a problem that it cannot be applied to gallium nitride based semiconductors.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a surface emitting type light emitting device which has a fast rising response of laser light emission and which can be manufactured with high accuracy and good reproducibility. An object of the present invention is to provide a method for manufacturing a semiconductor laser and a surface emitting semiconductor laser. It is another object of the present invention to provide a surface emitting semiconductor laser having a wide range of material selection and excellent versatility, and a method for manufacturing the surface emitting semiconductor laser.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, for example, a report by Kapolnek et al. (Applied Physics Letters Vol. 71 p. 1204 (199)
As described in 7)), I got the idea that there is a method of forming a gallium nitride-based semiconductor on a dielectric thin film by epitaxial growth by using selective growth.
The present invention has been completed.

That is, a surface emitting semiconductor laser according to the present invention comprises an upper and lower spacer layer formed with an active layer interposed therebetween, and an upper and lower multilayer reflective film formed with the upper and lower spacer layers interposed therebetween. A current confinement layer formed on one or both of the upper and lower spacer layers, wherein the current confinement layer is made of a dielectric material, and the spacer layer formed after the current confinement layer is a current confinement layer. Characterized by being selectively grown from the openings.

Preferably, the current confinement layer is made of a dielectric mainly composed of silicon dioxide or a dielectric mainly composed of silicon nitride. It is preferable that the active layer and the spacer layer are formed of a material containing at least gallium nitride in the composition. Further, the active layer and the spacer layer may be formed of a material containing at least gallium arsenide in the composition.

A method of manufacturing a surface emitting semiconductor laser according to the present invention is directed to a surface emitting semiconductor laser in which a lower multilayer reflective film, a lower spacer layer, an active layer, an upper spacer layer, and an upper multilayer reflective film are sequentially formed on a substrate. Forming a thin film made of a dielectric material on the lower spacer layer and / or the upper spacer layer; an etching step of forming an opening in the dielectric thin film; A selective growth step of selectively growing a selective growth spacer layer in at least a region on the dielectric thin film necessary to maintain the reflection characteristics and the waveguide characteristics of the resonator. It is characterized by comprising.

In the surface-emitting type semiconductor laser of the present invention, a partially-opened dielectric current confinement layer is formed on a p-type GaN upper spacer layer, and then a GaN single crystal thin film is selected on the current confinement layer. Since a material structure required for a surface emitting laser is manufactured by growth, a current confined portion can be manufactured with high positional accuracy by a semiconductor process based on photolithography, and reproducibility is good. In addition, since the current confinement portion is insulative and the refractive index waveguide structure is constantly formed, the rising response of laser emission is fast.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface emitting semiconductor laser according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing the structure of a surface emitting semiconductor laser according to an embodiment of the present invention. FIG. 2 is a perspective view of the surface-emitting type semiconductor laser of FIG. 1, and FIG. 3 is a plan view of the surface-emitting type semiconductor laser of FIG. In addition, the broken line in FIG. 3 represents the cut surface in FIG.

The surface emitting semiconductor laser shown in FIG. 1 has an n-type AlN /
GaN lower semiconductor multilayer reflector 3, n-type GaN lower spacer layer 4, In _0.08 Ga _0.98 N / In _0.15 Ga _0.85 N
An active layer 5 formed of a quadrupole well and Al _0.2 Ga _0.8 N, a p-type GaN upper spacer layer 6, a current confinement layer 10 made of a SiO ₂ dielectric thin film, a selective growth spacer layer 7, Type AlN / GaN upper semiconductor multilayer reflector 8;
The p-side electrode 9 is sequentially laminated, and is etched and removed to a depth where the n-type GaN substrate 1 is exposed, thereby forming a post-shaped light control region. Then, the exposed n-type Ga
An n-side electrode 2 is formed on an N substrate.

[0015] Here, n-type AlN / GaN lower semiconductor multilayer reflective mirror 3, 1/4 of substantially the oscillation wavelength of AlN and GaN semiconductor film having n-type conductivity of the carrier concentration of 1 × 10 ¹⁸ cm ^-3 Optical thickness (466 ° for AlN, G
In the case of aN, A has an optical film thickness of 22 periods alternately so as to have 402 °) and an optical film thickness of approximately 1/4 of the oscillation wavelength.
This is a semiconductor multi-layer reflecting mirror on which an 1N film is laminated. The GaN lower spacer layer 4 is a GaN layer having a carrier concentration of 1 × 10 ¹⁸ cm ^{−3 and} an n-type conductivity and a thickness of 350 °. The active layer 5 is made of In _0.08 having a film thickness of 105 ° and 35 °, respectively.
It is formed of a quadrupole well of Ga _0.98 N / In _0.15 Ga _0.85 N and a p-type conductive Al _0.2 Ga _0.8 N film having a carrier concentration of 1 × 10 ¹⁸ cm ^-3 and a thickness of 200 °. The p-type GaN upper spacer layer 6 has a carrier concentration of 1 × 10 ¹⁸ cm.
GaN layer having a p-type conductivity of ⁻³ and a thickness of 200 °. The p-type AlN / GaN upper semiconductor multilayer reflector 8 is made of Al-type p-type conductivity having a carrier concentration of 1 × 10 ¹⁸ cm ^−3.
This is a semiconductor multilayer reflector in which N and GaN semiconductor films are alternately stacked for 26 periods so as to have an optical film thickness substantially equal to １ ／ of the oscillation wavelength.

The current confinement layer 10 made of a SiO ₂ dielectric thin film, which is a characteristic feature of the present invention, is formed to have a thickness of 1000 ° and to have a partially formed opening 11. A film having a p-type conductivity with a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ , which is selectively grown at least in a region necessary for maintaining the reflection and waveguide characteristics of the resonator from the opening 11 of the layer 10. It consists of a 760 ° GaN layer. The dielectric material refers to a material having an electrical conductivity that is at least two orders of magnitude lower than the electrical conductivity of a conductive GaN semiconductor, such as Al ₂ O ₃ , ZrO ₂ , and Mg.
O, MgF ₂ , LiF, LaF and the like are included. Here, SiO ₂ is used as the dielectric material, but silicon nitride may be used. Other dielectric materials can be used as long as they are stable under the temperature conditions during selective growth (furnace temperature, atmosphere). In addition, selective growth is partially defined by S
When epitaxially growing GaN on a GaN single crystal thin film covered with an iO ₂ film, by controlling the crystal growth conditions, it is possible not only to grow the crystal on the GaN crystal exposed on the surface but also to grow the GaN crystal exposed on the surface. This is a technique in which a crystal grows laterally from a part and a single crystal is formed on SiO ₂ .

The distance between the lower semiconductor multilayer reflector 3 and the upper semiconductor multilayer mirror 8 is set so that a resonator is formed, and the active layer 5 and the lower spacer layer are formed so that the optical film thickness becomes twice the oscillation wavelength. 4 and the thickness of the upper spacer layer 6. Further, the “antinode” of the standing wave generated in the laser resonator is adjusted to be located at the position of the quantum well in the active layer 5.

A current flows from the p-side electrode 9 to the n-side electrode 2, and is efficiently injected into the active layer through the opening 11 of the current constriction layer 10 in which the current path is narrowed by the dielectric SiO ₂ . In this manner, laser light having an oscillation wavelength of 410 nm can be extracted from above the surface-emitting type semiconductor laser.

Next, the manufacturing process of this surface emitting semiconductor laser will be described with reference to FIG.

As shown in FIG. 4A, an n-type G layer having a plane orientation (0001) is formed by metal organic chemical vapor deposition (MOCVD).
On an aN substrate 1, an n-type AlN / GaN lower semiconductor multilayer reflector 3, an n-type GaN lower spacer layer 4, and In _0.08 G
a _0.98 N / In _0.15 Ga _0.85 N quadrupole well and Al _0.2
An active layer 5 made of Ga _0.8 N and a p-type GaN upper spacer layer 6 are sequentially stacked.

Next, the substrate is taken out of the growth chamber, and FIG.
As shown in FIG. ₂ , after forming the SiO ₂ dielectric thin film, a resist mask is formed by photolithography in order to provide a partial opening 11, and S is formed by using buffered hydrofluoric acid.
Unnecessary portions of the iO ₂ dielectric thin film are selectively removed by etching.

Next, as shown in FIG.
50 ° C., growth pressure 50 Torr, atmosphere gas H ₂ 3 liter / min, source gas trimethylgallium 20 μmol /
The selective growth spacer layer 7 is epitaxially grown from the portion removed by etching under the condition that a thin film can be formed on the dielectric portion of the current confinement layer at a rate of 1.5 liters / minute of ammonia. In the multilayer film manufactured so far, only the periphery of the central portion functions as the light control region, and the left and right end portions are unnecessary. Therefore, the selective growth spacer layer 7 may be selectively grown laterally at least in a region necessary for maintaining the reflection characteristics and the waveguide characteristics of the resonator.

Next, as shown in FIG. 4D, a p-type A is formed on the p-type GaN selective growth spacer layer 7 by MOCVD.
The 1N / GaN upper semiconductor multilayer reflector 8 is stacked.

Next, as shown in FIG. 4E, a portion unnecessary for forming the surface emitting laser is removed by dry etching using a chlorine-based compound until the n-type GaN substrate 1 is exposed. I do.

Finally, as shown in FIG. 4F, a p-side electrode 9 (for example, Ni / Au) is
Is formed, and an n-side electrode 2 (for example, an alloy of Ti / Al) is formed on the exposed n-type GaN substrate 1 to complete the surface-emitting type semiconductor laser according to the first embodiment.

In the surface-emitting type semiconductor laser manufactured as described above, the dielectric current confinement layer 10 partially having the opening 11 is formed on the p-type GaN upper spacer layer 6, and then the selective growth method is used. Then, a GaN single crystal thin film is formed by selective growth on the current confinement layer 10 by selective growth, and a material structure required for a surface emitting laser is manufactured.
By the masking, the current confined portion can be manufactured with high positional accuracy, and the reproducibility is good. In addition, since the current confinement portion is insulative and the refractive index waveguide structure is constantly formed, the rising response of laser emission is fast.

The crystal growth technique by selective growth can be applied not only to gallium nitride-based materials but also to gallium arsenide-based materials, for example. It is possible to configure even in the case of.

[0028]

According to the present invention, there are provided a surface-emitting type semiconductor laser and a method for manufacturing a surface-emitting type semiconductor laser which can be manufactured with high accuracy and high reproducibility in response to rising of laser emission. Further, according to the present invention, there are provided a surface emitting semiconductor laser having a wide range of material selection and excellent versatility, and a method of manufacturing the surface emitting semiconductor laser.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a surface emitting semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a perspective view of the surface emitting semiconductor laser of FIG. 1;

FIG. 3 is a top view of the surface emitting semiconductor laser of FIG. 1;

FIG. 4 is a cross-sectional view illustrating a manufacturing process of the surface-emitting type semiconductor laser according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 n-type GaN substrate 2 n-side electrode 3 lower semiconductor multilayer reflector 4 n-type GaN lower spacer layer 5 active layer 6 p-type GaN upper spacer layer 7 p-type GaN selective growth spacer layer 8 upper semiconductor multilayer reflector 9 p-side Electrode 10 Current confinement layer 11 Opening

Claims (6)

[Claims] 1. A surface-emitting type semiconductor laser comprising upper and lower spacer layers formed with an active layer interposed therebetween, and upper and lower multilayer reflection films formed with the upper and lower spacer layers interposed therebetween, wherein one of the upper and lower spacer layers is provided. Alternatively, the current confinement layer includes a current confinement layer formed on both of them. The current confinement layer is made of a dielectric material, and a spacer layer formed after the current confinement layer is selectively grown from an opening of the current confinement layer. A surface-emitting type semiconductor laser, comprising: 2. The surface emitting semiconductor laser according to claim 1, wherein said current confinement layer is made of a dielectric containing silicon dioxide as a main component. 3. The surface-emitting type semiconductor laser according to claim 1, wherein the current confinement layer is made of a dielectric containing silicon nitride as a main component. 4. The surface emitting semiconductor laser according to claim 1, wherein the active layer and the spacer layer include at least gallium nitride in the composition. 5. The surface emitting semiconductor laser according to claim 1, wherein the active layer and the spacer layer include at least gallium arsenide in the composition. 6. A method for manufacturing a surface-emitting type semiconductor laser in which a lower multilayer reflective film, a lower spacer layer, an active layer, an upper spacer layer, and an upper multilayer reflective film are sequentially formed on a substrate. Alternatively, a dielectric thin film forming step of forming a thin film made of a dielectric material on the upper spacer layer; an etching step of forming an opening in the dielectric thin film; A selective growth step of performing selective growth on at least a region on the body thin film necessary to maintain the reflection characteristics and the waveguide characteristics of the resonator, wherein the current confinement layer is made of the dielectric material. A method for manufacturing a surface-emitting type semiconductor laser.