JPH08250802A - Semiconductor laser and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To easily cleave the cavity facets of GaN-based lasers. [Structure] 1) A laser layer structure is formed of a GaN-based material on a substrate in which a sapphire (Al ₂ O ₃ ) layer is formed on a Si wafer, and the cleaved surface of the silicon and the cleaved surface of the GaN-based material are parallel to each other. A semiconductor laser in which a cavity is formed by a cleavage plane of a GaN-based material, 2) a sapphire (Al ₂ O ₃ ) wafer is bonded onto a Si single crystal wafer, and the sapphire wafer is thinned to form a Ga
When the laser layered structure is formed with N-based material and the end face of the cavity is formed by cleavage, the plane orientation of the Si wafer surface and Al ₂ are adjusted so that the cleavage plane of Si and the cleavage surface of GaN-based material are parallel. O
_{3 A} method of manufacturing a semiconductor laser in which the plane orientation of the wafer surface and the crystal orientation relationship of both wafers at the time of the bonding are determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a gallium nitride (GaN) -based material (a crystalline system based on GaN such as Al _x Ga _1-x N, In _x Ga _1-x N) from blue to ultraviolet. The present invention relates to a short-wavelength semiconductor laser having an emission wavelength in the region and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, GaN-based materials have been actively researched and developed in response to the realization of high-luminance light-emitting diodes (LEDs) using them.

A single crystal of sapphire (Al ₂ O ₃ ) is used as a substrate for crystal growth when manufacturing an LED, and a GaN-based material crystal is formed by using this substrate by metal organic vapor phase epitaxy (MOVPE). By performing the growth, it is possible to obtain a high-grade GaN epitaxial crystal despite the very large lattice mismatch of about 16% between Al ₂ O ₃ and GaN.

When manufacturing a semiconductor laser,
As in the case of LEDs, it is necessary to adopt a double hetero structure as the layer structure of the epitaxial film, and to add it to create an optical resonator.

[0005]

In a typical laser [0006] While the surface obtained by cleavage are the end face of the resonator, Al ₂ O
₃ It is difficult to fabricate a resonator because the single crystal substrate has no cleavage.

An object of the present invention is to make it possible to easily fabricate a resonator in a GaN-based laser by cleavage.

[0007]

[Means for Solving the Problems] 1) To solve the above problems, 1) use a gallium nitride (GaN) -based material for laser irradiation on a substrate in which a sapphire (Al ₂ O ₃ ) layer is formed on a silicon (Si) wafer. A semiconductor laser in which a layered structure is formed, in which the cleaved surface of silicon and the cleaved surface of a gallium nitride-based material are parallel, and a cavity is formed by the cleaved surface of a gallium nitride-based material, or 2) silicon (Si) single crystal Sapphire (Al
₂ O ₃ ) wafer is adhered, a sapphire wafer is thinned, and a laser layer structure is formed on it with a gallium nitride (GaN) -based material. When the end face of the cavity is formed by cleavage, A method of manufacturing a semiconductor laser in which the plane orientation of the silicon wafer surface, the plane orientation of the sapphire wafer surface, and the crystal orientation relationship of both wafers at the time of bonding are determined so that the cleavage planes of the gallium nitride-based material are parallel, or 3) The silicon wafer surface is a cleaved surface of silicon.
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
001) plane, and the crystal orientation relationship between the silicon wafer and the sapphire wafer is such that the [111] direction of silicon and the [01-10] direction of sapphire are parallel to each other. 10) The method of manufacturing a semiconductor laser as described in 2 above, wherein the surface is used as a resonator, or 4) The silicon wafer surface is a cleavage plane of silicon.
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
001) plane, the crystal orientation relationship between the silicon wafer and the sapphire wafer is such that the [111] direction of silicon and the [-2110] direction of sapphire are parallel, and the (01-10) plane of gallium nitride-based material is 3. The method for manufacturing a semiconductor laser as described in 2 above, which uses as a resonator. 5) The silicon wafer surface is a cleaved surface of silicon.
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
1-12) plane, the crystal orientation relationship between the silicon wafer and the sapphire wafer is such that the [111] direction of silicon and the [-2110] direction of sapphire are parallel to each other. ) The method of manufacturing a semiconductor laser as described in 2 above, wherein the surface is used as a resonator, or 6) The silicon wafer surface is a cleavage plane of silicon.
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
1-12) plane, the crystal orientation relationship between the silicon wafer and the sapphire wafer is such that the [111] direction of silicon and the [0-111) direction of sapphire are parallel to each other. This is achieved by the method for manufacturing a semiconductor laser as described in 2 above, wherein the surface is used as a resonator.

[0008]

In the present invention, an Al ₂ O ₃ wafer is bonded onto a cleavable silicon single crystal wafer, the Al ₂ O ₃ wafer is polished to a thickness of about 10 μm, and a GaN-based material is formed on the wafer. MOVPE laser structure with epitaxial multilayer film
After the growth, the electrode is formed by the vapor deposition method, etc., and the resonator is produced by cleavage. The main points showing the characteristics in this case are as follows. Use a plane perpendicular to the (111) plane, which is the cleavage plane, of the silicon wafer, such as the (01-1) plane or the (-211) plane. The crystal orientation of epitaxially grown GaN is
Since it is determined by the plane orientation of the Al ₂ O ₃ wafer surface, the (111) plane, which is the cleavage plane of the silicon wafer, and the cleavage plane of the epitaxially grown GaN-based crystal are parallel to each other.
₂ O ₃ to adjust the silicon wafer and the Al ₂ O ₃ wafer crystal orientation relationship when the wafer plane orientation and wafer bonding. That is, the cleavage planes of GaN are (0001) plane, (01-10) plane, (2-1-1
There are three (0) planes, one of which is (1
11) Make it parallel to the surface.

Note: In electronic filings, the usual notation for surface index cannot be used, so it is usually placed above the number-the symbol is placed before the number. By making the cleaved surface of silicon and the cleaved surface of GaN parallel to each other in this way, it is possible to easily obtain a clean cleaved surface of a GaN-based crystal by utilizing the cleaving property of silicon. Can be produced. At this time, since the Al ₂ O ₃ wafer is as thin as about 10 μm, it does not hinder the cleavage.

[0010]

Embodiments of the present invention will be described below. The (01-1) plane will be described as an example of the silicon wafer surface, but another plane may be used as long as it is a plane perpendicular to the (111) plane which is the cleavage plane. That is, the (-211) plane, the (-321) plane, the (-541) plane, etc., and the high index plane located in the middle of these planes can be used.

The crystal orientation relationship at the time of adhering the silicon wafer and the Al ₂ O ₃ wafer is determined as follows. Where Al
_{The case where the 2} O ₃ wafer surface is the (0001) plane and the (01-12) plane will be described, but Al ₂ O ₃ and Ga
If the crystal orientation relationship of the N epitaxial film is known, the plane orientation during wafer bonding can be determined by the same method.

[0012] Example 1: Al ₂ O ₃ on the surface of the wafer (0001) If on the surface of the case Al ₂ O ₃ wafer using a surface a (0001) plane was grown GaN crystal, the GaN (0001) plane Grows. The cleavage planes perpendicular to the (0001) plane of GaN are the (2-1-10) and (01-10) planes.
The crystal orientation relationship with ₂ O ₃ is as follows.

[2-1-10] GaN // [01-10] Al ₂ O ₃ [01-10] GaN // [-2110] Al ₂ O ₃ Therefore, silicon (Si) wafer and Al ₂ O ₃ If [01-10] Al ₂ O ₃ // [111] Si is taken as the crystal orientation relationship when bonded to the wafer, the [2-1-10] plane of GaN becomes parallel to the cleavage plane of Si, This cleavage plane can be used as the end face of the resonator.

If the crystal orientation relationship between the Si wafer and the Al ₂ O ₃ wafer is [-2110] Al ₂ O ₃ // [111] Si, the [01-10] plane of GaN is It becomes parallel to the cleavage plane of Si, and this cleavage plane can be used as the end face of the resonator.

Example 2: On the surface of an Al ₂ O ₃ wafer (01-12)
When using a plane When a GaN crystal is grown on the (01-12) plane of an Al ₂ O ₃ wafer, the (2-1-10) plane of GaN grows. Cleavage planes perpendicular to the (2-1-10) plane of GaN are the (0001) and (01-10) planes.
The crystal orientation relationship with ₂ O ₃ is as follows.

[0001] GaN // [0-111] Al ₂ O ₃ [01-10] GaN // [-2110] Al ₂ O ₃ Therefore, the crystal at the time of adhesion between the Si wafer and the Al ₂ O ₃ wafer If the orientation relationship is [0-111] Al ₂ O ₃ // [111] Si, the [0001] plane of GaN is parallel to the cleavage plane of Si,
This cleavage plane can be used as the end face of the resonator.

If the crystal orientation relationship between the Si wafer and the Al ₂ O ₃ wafer is [-2110] Al ₂ O ₃ // [111] Si, the [01-10] plane of GaN is It becomes parallel to the cleavage plane of Si, and this cleavage plane can be used as the end face of the resonator.

Next, an embodiment of the laser of the present invention will be described together with its manufacturing method with reference to FIG. The case where the (01-1) plane is used as the Si wafer surface and the (01-12) plane is used as the Al ₂ O ₃ wafer surface and the (0001) plane of GaN is used as the end face of the resonator is described. The surface can be manufactured by the same procedure.

In FIG. 1 (A), a thickness of (01-1) of 400 μm
Surface of Si wafer 1 and 400 μm thick (01-12) surface of Al ₂ O
₃ Bond the wafer 2. At this time, [111] direction of Si and Al
Make the [0-111] direction of ₂ O ₃ parallel.

Further, the adhesion at this time is performed as follows, for example. When a mirror-polished Al ₂ O ₃ wafer and a mirror-polished Si wafer are stacked at room temperature and the edges of the wafer are pressed lightly with tweezers, the bonding area due to the Van der Waals force spreads over the entire surface of the wafer, and it is fairly firm. It will be in a temporarily bonded state.

Next, the temporarily bonded wafers are set to 400 to 10
By heat treatment at a temperature of 00 ° C, a chemical reaction takes place at the bonded interface due to the Van der Waals force, and the state becomes strong at the atomic level.

In FIG. 1B, the Al ₂ O ₃ wafer 2 is polished to a thickness of 10 μm. In Fig. 1 (C), an n-type (n-) AlGaN layer 3 with a thickness of 5 μm and a thickness of 0.2 on the Al ₂ O ₃ wafer 2.
A μm InGaN layer 4 and a 2 μm thick p-type (p-) AlGaN layer 5
Epitaxial growth is performed in this order by the MOVPE method. The AlGaN and InGaN surfaces of the grown film are (2-1-10) planes.

In FIGS. 1D and 1E, a ridge is formed so that the [111] direction of Si becomes the stripe direction, and the p-side electrode is formed.
6 and the n-side electrode 7 are formed. In Fig. 1 (F),
Cleavage is performed on the (111) plane to form a resonator with a length of 300 μm. At this time, the end faces of AlGaN and InGaN are cleaved faces.
Since it is a (0001) plane, it is possible to fabricate a resonator having a clean cleavage plane.

Next, the case of using another surface relationship will be described. The silicon wafer surface is a cleaved surface of silicon
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
001) plane, and the crystal orientation relationship between the silicon wafer and the sapphire wafer is such that the [111] direction of silicon and the [01-10] direction of sapphire are parallel to each other. 10) The surface is used as a resonator (corresponding to claim 3). The silicon wafer surface is a cleaved surface of silicon
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
001) plane, and the crystal orientation relationship between a silicon wafer and a sapphire wafer is such that the [111] direction of silicon is parallel to the [-2110] direction of sapphire, and the (01-10) plane of gallium nitride-based material is Is used as a resonator (corresponding to claim 4). The silicon wafer surface is a cleaved surface of silicon
It is a plane perpendicular to the (111) plane, and the sapphire wafer plane is (0
1-12) plane, and the crystal orientation relationship between a silicon wafer and a sapphire wafer is such that the [111] direction of silicon and the [-2110] direction of sapphire are parallel to each other. ) The surface is used as a resonator (Claim 5)
Correspondence).

Although the ridge type laser has been described in the embodiment, a resonator can be manufactured by a similar method to a laser having another structure such as an embedded laser. The structure of the epitaxial layer is not limited to the AlGaN / InGaN / AlGaN double heterostructure, but the present invention can be applied to a laser having a more complicated structure such as a strained multiple quantum well (MQW).

[0026]

According to the present invention, in a GaN-based laser, a resonator can be manufactured using a cleavage plane that can be easily obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

[Explanation of symbols]

1 Silicon (Si) substrate 2 Sapphire (Al ₂ O ₃ ) substrate 3 n-AlGaN layer 4 InGaN layer 5 p-AlGaN layer 6 p-side electrode 7 n-side electrode

Claims (6)

[Claims] 1. Sapphire (A) on a silicon (Si) wafer
On the substrate on which the l ₂ O ₃ ) layer is formed, gallium nitride-based (GaN)
A semiconductor laser characterized in that a layer structure of a laser is formed of a material, a cleaved surface of silicon and a cleaved surface of a gallium nitride-based material are parallel to each other, and a cavity is formed by the cleaved surface of a gallium nitride-based material. 2. A sapphire (Al ₂ O ₃ ) wafer is bonded onto a silicon (Si) single crystal wafer, the sapphire wafer is thinned, and a laser layer structure is formed on the sapphire wafer with a gallium nitride (GaN) -based material. , When the end face of the resonator is formed by cleavage, the surface orientation of the silicon wafer surface is adjusted so that the cleavage surface of silicon and the cleavage surface of gallium nitride-based material are parallel.
A method of manufacturing a semiconductor laser, wherein a plane orientation of a sapphire wafer surface and a crystal orientation relationship between both wafers at the time of bonding are determined. 3. The silicon wafer surface is a surface perpendicular to a (111) plane which is a cleavage plane of silicon, and the sapphire wafer surface is a (0001) plane, and the crystal orientation relationship between the silicon wafer and the sapphire wafer is silicon. The [111] direction of is parallel to the [01-10] direction of sapphire, and the (2-1-10) plane of gallium nitride-based material is used as a resonator. Manufacturing method of semiconductor laser. 4. The silicon wafer surface is a surface perpendicular to a (111) plane which is a cleavage plane of silicon, and the sapphire wafer surface is a (0001) plane, and the crystal orientation relationship between the silicon wafer and the sapphire wafer is silicon. The [111] direction of sapphire and the [-2110] direction of sapphire are parallel to each other, and the (01-10) plane of gallium nitride-based material is used as a resonator. Production method. 5. A crystal orientation relationship between a silicon wafer and a sapphire wafer, wherein the silicon wafer surface is a plane perpendicular to a (111) plane which is a cleavage plane of silicon, and a sapphire wafer surface is a (01-12) plane. Has a relationship in which the [111] direction of silicon and the [-2110] direction of sapphire are parallel,
The method of manufacturing a semiconductor laser according to claim 9, wherein the (01-10) plane of the gallium nitride based material is used as a resonator. 6. The crystal orientation relationship between the silicon wafer and the sapphire wafer, wherein the silicon wafer surface is a plane perpendicular to the (111) plane which is the cleavage plane of silicon, and the sapphire wafer surface is the (01-12) plane. Has a relationship that the [111] direction of silicon and the [0-111) direction of sapphire are parallel,
3. The method for manufacturing a semiconductor laser according to claim 2, wherein the (0001) plane of gallium nitride based material is used as a resonator.