JPH10275955A - Semiconductor laser diode and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] To obtain a high performance semiconductor laser diode. Kind Code: A1 Abstract: In a semiconductor laser diode having a multi-layer of a gallium nitride-based compound semiconductor forming a laser element on a main surface of a single crystal sapphire plate, two back-facing end faces forming a resonator of laser light in the multi-layer. Is composed of a cleavage plane along a direction inclined from the C plane of the single crystal sapphire plate by 59.5 to 60.5 ° and inclined from the R plane by 2.5 to 3.5 °.

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 short wavelength side in a visible region, particularly in a blue region to an ultraviolet region.

[0002]

2. Description of the Related Art A semiconductor laser diode is used as a light emitting element for various applications, and there is a structure in which a laser element composed of multiple layers of semiconductors is formed on the surface of a single crystal sapphire plate.

As shown in FIG. 1, a semiconductor laser diode is formed by forming a semiconductor multi-layer 3 constituting a laser element on the surface of a single-crystal sapphire plate 1 via a buffer layer 2 as shown in FIG. In this semiconductor laser diode, the oscillation efficiency of the laser can be improved by making the back end faces 3a, 3a forming the resonator of the laser light smooth and increasing the parallelism.

Japanese Patent Laid-Open Publication No. Hei 7-297495 discloses a method of manufacturing this semiconductor laser diode. After a multi-layer 3 is formed on the A-plane (11-20) of a single-crystal sapphire substrate, the single-crystal sapphire substrate is By cleaving along <0001> and dividing, the back-facing end face 3 of the multilayer 3
It has been proposed to improve the oscillation efficiency of a semiconductor laser diode by using a and 3a as precise mirror surfaces.

[0005]

However, when single-crystal sapphire is cleaved along the C-axis as shown in the above-mentioned Japanese Patent Application Laid-Open No. Hei 7-297495, a stable cleavage plane cannot be obtained. Surface accuracy of the opposed end surfaces 3a, 3a of
Since the degree of parallelism cannot be increased, a laser diode with good yield and good oscillation efficiency cannot be obtained.

Accordingly, the present invention improves the accuracy of the cleavage plane of sapphire, thereby improving the parallelism and the surface accuracy of the back-facing end faces of the multiple layers constituting the resonator, and improving the laser oscillation efficiency. It is an object of the present invention to obtain a semiconductor laser diode with a high yield.

[0007]

According to the present invention, there is provided a single crystal sapphire plate having, on a main surface thereof, a multi-layer of gallium nitride based compound semiconductor forming a laser element, and forming a laser beam resonator in the multi-layer. The two end faces are characterized by being composed of a cleavage plane inclined by 59.5 to 60.5 ° from the C plane of the single crystal sapphire plate and 2.5 to 3.5 ° from the R plane.

Further, according to the present invention, after a multi-layer of a gallium nitride-based compound semiconductor forming a laser element is formed on a single-crystal sapphire substrate, the single-crystal sapphire substrate and the multi-layer are formed from the C-plane of the sapphire. The semiconductor laser diode is manufactured by a process of dividing the semiconductor laser diode into a large number of pieces along a direction inclined by 5 to 60.5 ° and inclined by 2.5 to 3.5 ° from the R plane.

[0009]

Generally, the cleavage plane of a gallium nitride compound semiconductor and the R plane of single crystal sapphire are inclined by 2.5 to 3.5 °. Therefore, according to the present invention, after forming the multiple layers of the semiconductor, the single-crystal sapphire substrate is removed from the C-plane by 59.5.
By dividing along a direction inclined by about 60.5 ° and inclined by 2.5 to 3.5 ° from the R plane, this direction coincides with the cleavage plane of the gallium nitride-based compound semiconductor. It can be a smooth surface. For this reason, if this division surface is a back-facing end surface forming a resonator, the laser oscillation efficiency of the semiconductor laser diode can be improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
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 ≦
A description will be given of a laser diode comprising 1,0 ≦ y ≦ 1).

As shown in a perspective view in FIG. 1 and a cross-sectional view in FIG. 2, the semiconductor laser diode of the present invention includes a buffer layer 2 made of an AlN layer on a main surface 11 of a single crystal sapphire plate 1. On the layer 2, there is provided a semiconductor multi-layer 3 forming a laser element.

The multi-layer 3 includes an n ⁺ layer 31 made of a Si-doped n-type GaN layer provided on the entire surface of the buffer layer 2, an electrode 41 provided on the n ⁺ layer 31, and a portion other than the electrode 41. N layer 32 composed of a Si-doped Al _0.1 Ga _0.9 N layer and active layer 3 composed of a silicon-doped GaN layer
3, a p layer 34 made of magnesium-doped the Al _0.1 Ga _0.9 N layer, a SiO ₂ layer 35 covering the, SiO ₂
It is composed of an electrode 42 provided in the window of the layer 35.

As shown in FIG. 1, the two opposite end faces 12 and 12 of the single crystal sapphire plate 1
9.5 to 60.5 ° inclination, and 2.5 to 3.5 from the R plane
° are divided along the inclined direction, and the rear facing end faces 3a, 3a of the multi-layer 3 are the end faces 12,
12 and the same plane.

As will be described later in detail, the semiconductor laser diode according to the present invention, after forming the multi-layer 3 on a single crystal sapphire substrate, is tilted by 59.5 to 60.5 ° from the C plane and the R plane. By splitting along a direction inclined by 2.5 to 3.5 ° from, efficient production can be achieved.

At this time, as shown in the schematic diagram of FIG. 3, since the single crystal sapphire plate 1 is divided along a direction inclined from the R plane, the divided surface 12 has a minute step shape. However, since the cleavage plane of the gallium nitride-based compound semiconductor exactly coincides with the above-mentioned division direction, the back-facing end face 3
a and 3a can be very smooth and highly parallel surfaces. As a result, when a voltage is applied between the two electrodes 41 and 42 to oscillate laser light, the back-facing end faces 3a, 3a
Since a resonator is formed between a, the oscillation efficiency of laser light can be improved.

Hereinafter, a method of manufacturing the semiconductor laser diode shown in FIGS.

First, as shown in FIG. 5, a single-crystal sapphire substrate 10 whose main surface 11 has an A-plane (11-20) is prepared.

Here, the crystal structure of single crystal sapphire is
As shown in FIG. 4, C is a hexagonal system,
Axis perpendicular thereto C plane (0001), A axis extending radially from the C axis to the three-way (a ₁ axis, a ₂ axis, a _3-axis) perpendicular A plane, respectively (11-20), C axis There is an R-plane (1-102) having a certain angle with respect to and an R-axis perpendicular thereto. That is, as shown in FIG. 5, in the case of the single crystal sapphire substrate 10 having the main surface 11 as the A surface, the R surface exists as a cross section perpendicular to the main surface 11. The directions of these planes and axes can be analyzed by X-ray diffraction.

After the single crystal sapphire substrate 10 is organically washed, it is set in a crystal growth section of a crystal growth apparatus. After evacuating the inside of the apparatus, hydrogen is supplied and about 1 hour in a hydrogen atmosphere.
The temperature is raised to 200 ° C. to remove the hydrocarbon-based gas attached to the surface of the single-crystal sapphire substrate 10.

Next, the temperature of the single crystal sapphire substrate 10 is lowered to about 600 ° C., and trimethyl aluminum (T
MA) and ammonia (NH ₃ ) to grow an AlN layer on the substrate to a thickness of about 50 nm,
And Next, only the supply of TMA is stopped, the temperature of the substrate is increased to 1040 ° C., and trimethylgallium (TMG)
And silane (SiH ₄ ) to supply Si-doped n-type Ga
An n ⁺ layer 31 composed of an N layer is grown.

Once the single crystal sapphire substrate 10 is taken out of the growth furnace, a part of the surface of the n ⁺ layer 31 is masked with SiO ₂ , returned to the growth furnace again, evacuated and supplied with hydrogen and NH _3. And raise the temperature to 1040 ° C. Next, T
MA, TMG and SiH ₄ are supplied, and a portion not masked with SiO ₂ is doped with 0.5 μm-thick Si-doped Al.
_{A 0.1} Ga _0.9 N layer is formed to form an n layer 32.

Next, TMG and SiH ₄ are supplied to form an active layer 33 by forming a silicon-doped GaN layer having a thickness of 0.2 μm. Next, TMA, TMG and Cp ₂ Mg (biscyclobentadienyl magnesium) were supplied,
0.5 μm thick magnesium-doped Al _0.1 Ga _0.9
A p layer 34 made of an N layer is formed.

Next, the SiO ₂ used as the mask is removed by a hydrofluoric acid-based etchant, and the SiO _{2 is}
After the layer 35 is deposited, a rectangular window of 1 mm long and 80 μm wide is opened, moved to a vacuum chamber, and the p-layer 34 is irradiated with an electron beam. By this electron beam irradiation, the p-layer 34 showed p-conduction.

Next, a portion corresponding to the window of the p layer 34 and n ⁺
On the layer 31, metal electrodes 41 and 42 are respectively formed.

A large number of multiple layers 3 constituting the above-mentioned laser element are formed on one single crystal sapphire substrate 10. Then, by dividing the single crystal sapphire substrate 10 and the multilayer 3 at the same time, individual semiconductor laser diodes shown in FIGS. 1 and 2 can be obtained.

When performing this division, the rear facing end faces 3a, 3a of the multilayer 3 and the end faces 12, 12 of the single crystal sapphire plate 1
Is 59.5 to 60.5 ° from the C plane as shown in FIG.
It is divided along the direction inclined (2.5 to 3.5 ° from the R plane) (two-dot chain line), and the other end face is cut and cut by a diamond cutter or the like.

The method of dividing in the above direction is as follows. A crack line is drawn on the surface of the single crystal sapphire substrate 10 along the above direction with a diamond pen, and a pre-stress is applied in a direction in which the crack line is expanded. Can grow and split. Alternatively, division may be performed by inducing thermal stress in a cleavage direction by a laser beam or a heating wire (including a heating wire such as a nichrome wire). Alternatively, a groove having a depth of 10 to 200 μm may be formed on the back surface of the single-crystal sapphire substrate 10 and divided along the groove.

Thus, from the C plane, 59.5 to 60.5
By splitting along the direction inclined at an angle of 2.5 ° to 3.5 ° from the R-plane, the back-facing end faces 3a and 3a of the multi-layer 3 forming the semiconductor laser diode are exactly the same as the cleavage plane of the gallium nitride compound. It is possible to have a plane that is coincident, extremely smooth and highly parallel. As a result, a semiconductor laser diode having high oscillation efficiency can be obtained.

Actually, the main surface 11 of the single-crystal sapphire substrate 10 having a thickness of 225 to 275 μm is defined as an A-plane, GaN is grown on the main surface 11, and then the substrate is removed from the sapphire C-plane by 59.5. When divided along a direction inclined by 60.5 ° and inclined by 2.5-3.5 ° from the R-plane, it is easy to divide and the opposed single surfaces 3a, 3a of the multilayer 3
Was able to be a very smooth and highly parallel surface.
However, if the substrate is divided in a direction other than the above, it is difficult to divide the substrate with high accuracy, and it is extremely difficult to obtain cleavage planes in parallel.

The main surface 11 of the sapphire substrate 10 is not necessarily required to be the A surface. For example, as shown in FIG. 7, the main surface 11 may be a C surface. In this case, R
Although the plane is not perpendicular to the main surface 11 but has an angle of about 57.62 °, it is still 59.5 to 60.5 ° from the C plane.
When divided along the direction inclined and at an angle of 2.5 to 3.5 ° from the R plane, it can be easily divided, and the facing single surface 3 of the multilayer 3
a and 3a can be smooth surfaces.

Further, the main surface 11 can be a surface other than the A-plane and the C-plane.
There was no effect on the crystal orientation of N.

The sapphire substrate 10 can be obtained by various growth methods. By growing the substrate by the EFG method, a substrate having a cleavage plane set efficiently can be easily obtained.

For example, the single-crystal sapphire substrate 10 shown in FIG. 8 is disk-shaped and has an orientation flat forming a reference plane 10a in a part of the periphery thereof.
Are formed perpendicular or parallel to the R-plane. Further, the single-crystal sapphire substrate 1 shown in FIG. 9 is rectangular, and has one reference plane 10a formed parallel to the R plane and the other reference plane 10b formed perpendicular to the R plane.

As described above, by forming the reference surfaces 10a and 10b perpendicular or parallel to the R surface, the direction of the R surface can be identified, and the area of the substrate can be maximized when dividing. Can be used.

[0035]

As described above, according to the present invention, in a semiconductor laser diode having a multi-layer of a gallium nitride-based compound semiconductor forming a laser element on a main surface of a single crystal sapphire plate, a laser in the multi-layer is used. Two back-facing end faces forming an optical resonator are tilted by 59.5 to 60.5 degrees from the C plane of the single crystal sapphire plate, and 2.5 to 3.0.5 from the R plane.
By having a cleavage plane along the direction inclined by 5 °,
The surface accuracy and parallelism of the back end face of the multilayer can be increased, and the laser oscillation efficiency can be improved.

Further, according to the present invention, after forming a multi-layer of a semiconductor forming a laser element on a single-crystal sapphire substrate, the single-crystal sapphire substrate and the multi-layer are separated from the C-plane of sapphire by 59.5 to 59.5. By manufacturing a semiconductor laser diode from a process of dividing into a large number of pieces along a direction inclined at 60.5 ° and inclined at 2.5 to 3.5 ° from the R plane, a high performance semiconductor can be achieved in an extremely simple process. Laser diodes can be manufactured.

According to the present invention, it is possible to obtain a high-performance semiconductor laser diode capable of emitting light in the short wavelength side in the visible region, particularly in the blue region to the ultraviolet region.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a semiconductor laser diode of the present invention.

FIG. 2 is a sectional view taken along line XX in FIG.

FIG. 3 is a schematic view showing an end face of the semiconductor laser diode of the present invention.

FIG. 4 is a diagram showing a basic crystal structure of single crystal sapphire.

FIG. 5 is a perspective view showing a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention.

FIG. 6 is a perspective view showing a dividing direction when manufacturing the semiconductor laser diode of the present invention.

FIG. 7 is a perspective view showing a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention.

8A and 8B show a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention, wherein FIG. 8A is a plan view and FIG. 8B is a side view.

9A and 9B show a single crystal sapphire substrate used when manufacturing the semiconductor laser diode of the present invention, wherein FIG. 9A is a plan view and FIG. 9B is a side view.

[Explanation of symbols]

 1: Single crystal sapphire plate 11: Main surface 12: End surface 2: Buffer layer 3: Multilayer 3a: Backward end surface 10: Single crystal sapphire substrate

Claims (2)

[Claims] 1. A multi-layer of a gallium nitride-based compound semiconductor constituting a laser device on a main surface of a single crystal sapphire plate,
The two end faces forming the resonator of the laser beam in the multi-layer are 59.5-6 cm from the C-plane of the single crystal sapphire plate.
A semiconductor laser diode comprising a cleavage inclined by 0.5 ° and inclined by 2.5 to 3.5 ° from an R plane. 2. After forming a multi-layer of a gallium nitride-based compound semiconductor forming a laser element on a single-crystal sapphire substrate, the single-crystal sapphire substrate and the multi-layer are formed from a C-plane of sapphire at 59.5-60. A method for manufacturing a semiconductor laser diode, comprising: dividing a semiconductor laser diode into a large number of pieces along a direction inclined by 5 ° and inclined by 2.5 to 3.5 ° from an R plane.