JPH07202325A - Gallium nitride compound semiconductor laser diode - Google Patents

Abstract

PURPOSE:To improve laser oscillation efficiency by constituting a resonator of an uppermost first electrode layer, a lowermost second electrode layer and multiple layers therebetween and outputting a laser to a direction perpendicular to the electrode layers. CONSTITUTION:Multiple layers 3 to 6 comprising gallium nitride compound semiconductor of a double hetero junction structure ((AlxGa1-x)yIn1-yN: 0<=x<=1, 0<=y<=1) are laminated on a sapphire substrate 1, wherein a first electrode layer 8 made of a reflection film is formed on the uppermost layer 6 and a second electrode layer 9 of the reflection film is formed on the lowermost layer 3 which is exposed at a hole 1a formed on the sapphire substrate 1. The first electrode layer 8, the second electrode layer 9 and the multiple layers 3 to 6 between both electrode layers 8, 9 constitute a laser resonator for outputting a laser in a direction perpendicular to the electrode layers 8, 9. Thus oscillation efficiency of the laser is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser diode capable of emitting light in a single visible wavelength, particularly in the blue region to the violet region and the ultraviolet region.

[0002]

2. Description of the Related Art Conventionally, a laser diode described in Japanese Patent Laid-Open No. 4-242985 has been proposed. The laser diode is indium gallium aluminum phosphide (InGaAlP)
It is made of a system crystal, and a layer without addition of impurities is used for the active layer.

[0003]

This laser diode is obtained by epitaxially growing a gallium nitride compound semiconductor on a sapphire substrate. However,
When manufacturing a laser diode, it is necessary to obtain a precise mirror surface, but the cleavage direction for obtaining a precise mirror surface has not yet been found. Since a precise mirror surface cannot be obtained, there is a problem that the laser oscillation efficiency is low.

The present invention has been made to solve the above problems, and an object thereof is to improve the parallelism and surface accuracy of both end faces constituting a resonator in a gallium nitride-based compound semiconductor laser diode. Is to improve the oscillation efficiency of the laser.

[0005]

The structure of the invention for solving the above-mentioned problems is a gallium nitride compound semiconductor having a double heterojunction structure in which an active layer is sandwiched by layers having a forbidden band width larger than the forbidden band width. ((Al _x Ga _1-x ) _y In _1-y N: 0 ≦ x ≦ 1,
0 ≦ y ≦ 1), a sapphire substrate and a gallium nitride compound semiconductor ((Al _x Ga _1-x) formed in a double heterojunction structure directly or with a buffer layer interposed on the sapphire substrate. ) _y In _1-y N: 0≤x≤1,0≤y
≦ 1) stacked multilayers, the first electrode layer formed of a reflective film on the uppermost layer of the multilayer, and the reflection formed on the exposed lowermost layer of the multilayer in the hole formed on the sapphire substrate. A second electrode layer formed of a film, the first electrode layer and the second electrode layer, and a multi-layer between them form a resonator, and output a laser in a direction perpendicular to the electrode layer. It is characterized by doing so.

[0006]

As described above, the present invention forms a multi-layer of gallium nitride compound semiconductor on the main surface of the sapphire substrate, forms a laser element by the multi-layer, and forms a hole in the sapphire substrate from the back surface. A mirror-like second electrode layer is formed on the lowermost layer of the multilayer exposed in the hole, and a mirror-like first electrode layer is formed on the uppermost layer. Therefore, the two mirror surfaces can form a resonator in a direction perpendicular to the main surface of the sapphire substrate. The end surface of this resonator can be formed into a mirror surface by vapor deposition or the like, and high surface accuracy can be obtained, so that the efficiency of laser output can be improved.

[0007]

EXAMPLES The present invention will be described below based on specific examples.

FIG. 1 is a sectional view showing the structure of a semiconductor laser diode using a sapphire substrate. In FIG. 1, a sapphire substrate 1 having a (1,1, -2,0) plane (a-plane) as a crystal growth plane is subjected to organic cleaning and then installed in a crystal growth unit of a crystal growth apparatus. After evacuation of the growth furnace, hydrogen is supplied and 1200
Raise the temperature to about ℃. As a result, the hydrocarbon gas attached to the surface of the sapphire substrate 1 is removed to some extent.

Next, the temperature of the sapphire substrate 1 is lowered to about 600 ° C., trimethylaluminum (TMA) and ammonia (NH ₃ ) are supplied, and the AlN layer 2 having a film thickness of about 50 nm is formed on the sapphire substrate 1. To form.

Next, the supply of TMA is stopped and the substrate temperature is adjusted.
Raise to 1040 ℃, trimethylgallium (TMG) and silane
(SiH ₄ ) is supplied to grow the Si-doped n-type GaN layer 3 (n ⁺ layer) (bottom layer).

Next, TMA and TMG and silane (SiH ₄ ) were supplied to the Si-doped Al _0.1 Ga _0.9 N layer 4 having a thickness of 0.4 μm.
(N layer) is formed.

Next, by supplying TMG, GaN having a thickness of 0.2 μm is formed.
Layer 5 (active layer) is grown.

Next, by supplying TMA, TMG and Cp ₂ Mg,
0.4 μm thick magnesium-doped Al _0.1 Ga _0.9 N layer 6
(P layer) (uppermost layer) is formed.

Next, SiO _{2 is formed} on the Al _0.1 Ga _0.9 N layer 6 (p layer).
After depositing the layer 7, a window 7A is opened in 1 mmφ. Further, a hole 1A was made in 1 mmφ from the back surface b side of the sapphire substrate 1 by reactive ion etching (RIE) to expose the Si-doped n-type GaN layer 3.

Then, it was transferred to a vacuum chamber and the magnesium-doped Al _0.1 Ga _0.9 N layer 6 (p layer) and GaN were deposited.
The layer 5 (active layer) is subjected to electron beam irradiation treatment. By this electron beam irradiation, the Al _0.1 Ga _0.9 N layer 6 (p layer) and the GaN layer 5
(Active layer) and p-type conduction.

Typical electron beam irradiation treatment conditions are shown in the table.

[Table 1]

Next, the window 7A of the Al _0.1 Ga _0.9 N layer 6 (p layer) is formed.
2000 Å aluminum electrode layer (first
Electrode layer) 8 was formed. Also, exposed in the hole 1A
An aluminum electrode layer (second electrode layer) 9 having a thickness of 800 Å was formed on the Si-doped n-type GaN layer 3. The aluminum electrode layers 8 and 9 become mirror surfaces on both ends of the laser resonator.

A large number of the above-mentioned elements are formed on one sapphire substrate 1, and each element is cut with a diamond cutter. Then, in each element, the aluminum electrode layer 8
By applying a voltage to the aluminum electrode layer 9 and the aluminum electrode layer 9, the laser diode oscillates in the X-axis direction (direction perpendicular to the surface of the sapphire substrate 1). The oscillated laser is output from the aluminum electrode layer 9 side having a reflectance of 80%.
The aluminum electrode layer 8 can have a reflectance of 100%.

Thus, a laser diode having a vertical resonator can be obtained.

The electrode layer on the laser output side can be formed of, for example, a multi-layer of GaN having a thickness of 350 Å and AlGaN having a thickness of 350 Å instead of aluminum.
The reflectance can be controlled by the number of layers and the thickness of the multiple layers. Further, this electrode layer may be composed of a multi-layer of SiO ₂ / TiO ₂ . Also in this case, the reflectance can be controlled by the number of layers and the thickness of the layers.

The etching time of the sapphire substrate 1 can be shortened by polishing the sapphire substrate 1 from the back surface a side and then etching.

The laser diode described above can emit dots by forming a large number of dot-shaped electrodes on one surface, and can be used as a flat dot matrix display.

[Brief description of drawings]

FIG. 1 relates to a specific example of the present invention formed on a sapphire substrate ((Al _x Ga _1-x ) _y In _1-y N: 0 ≦ x ≦ 1,0 ≦ y ≦ 1)
FIG. 3 is a cross-sectional view showing the configuration of a semiconductor laser diode.

[Explanation of symbols]

1 ... Sapphire (11-20) face substrate 2 ... AlN buffer layer 3 ... GaN layer (n ⁺ layer) (bottom layer) 4 ... Al _0.1 Ga _0.9 N layer (n layer) 5 ... GaN layer (active layer) 6 ... Al _0.1 Ga _0.9 N layer (p layer) (uppermost layer) 7 --- SiO ₂ layer 8 ... Aluminum electrode layer (first electrode layer) 9 ... Aluminum electrode layer (second electrode layer)

Front page continuation (71) Applicant 591014950 Amano Hiro Ainoyama, Nagoya, Meito-ku, Yamanote 2-chome 104 Takara Mansion Yamanote 508 (72) Inventor Norikatsu Koide Aichi Prefecture Nishikasugai-gun Kasuga-cho 1 Ochiai, Nagahata Toyoda Gosei Incorporated (72) Inventor Shiro Yamazaki 1 Ochiai, Nagachibata, Kasuga-cho, Nishikasugai-gun, Aichi Toyoda Gosei Co., Ltd. (72) Inventor Junichi Umezaki 1-Ichi, Nagahata, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Toyoda Gosei Co., Ltd. (72) Inventor, Isamu Akasaki, 1-3-1, Joshi, Nishi-ku, Nagoya, Aichi Prefecture 38-805 (72) Inventor, Hiroshi Amano 2-21, Kamioka-cho, Meito-ku, Nagoya, Aichi Prefecture, Nijigaoka East Complex, Room No. 103, Bldg.

Claims (1)

[Claims] 1. A gallium nitride-based compound semiconductor ((Al _x Ga _1-x ) _y In _1-y N: having a double heterojunction structure in which an active layer is sandwiched between layers having a forbidden band width larger than the forbidden band width. 0 ≦ x ≦ 1,0
≦ y ≦ 1), a sapphire substrate, and a gallium nitride-based compound semiconductor ((Al _x Ga _{1- x} ) _y In _1-y N: 0 ≤x≤1,0≤y
≦ 1) laminated multilayer, a first electrode layer formed of a reflective film on the uppermost layer of the multilayer, and formed on the exposed lowermost layer of the multilayer in a hole formed on the sapphire substrate Second formed of a reflective film
An electrode layer, and a resonator is constituted by the first electrode layer, the second electrode layer, and a multi-layer between them, and a laser is output in a direction perpendicular to the electrode layer. A gallium nitride-based compound semiconductor laser diode characterized by: