JPS599989A - Optical semiconductor element - Google Patents

Abstract

PURPOSE:To obtain a long life, by providing a BN film on a crystal surface which transmits or reflects light, thereby effectively dissipating heat yielded at an end surface. CONSTITUTION:On an N type substrate 10, N type Ga0.65Al0.35As 11, a nonadded Ga0.95Al0.15As active layer 12, P type Ga0.65Al0.35As 13 and N type GaAs 14 are laminated. An Si3H4 mask 15 is applied, a window is provided in a stripe shape, and a Zn diffused layer 19 reaching the layer 13 is formed. The mask is removed, and a P side ohmic electrode 16 is attached, and an N side ohmic electrode 17 is attached to the back surface of the substrate. A BN film 18 is deposited on the side surface of the device, which is to become a mirror surface after cleavage, by a CVD method. In this constitution, the life of the device is made longer than the life obtained by using an SiO2 film.

Description

[Detailed description of the invention] Present invention d: relates to an optical semiconductor device.

Light-emitting elements such as semiconductor lasers and light-emitting diodes
In light-receiving elements such as photodiodes, the quality of the crystal planes through which light is transmitted or reflected greatly influences the performance of the element.

FIG. 1 (al) shows an example of a striped semiconductor laser.

An n-type cladding layer 2. is formed on an n-type substrate 1. Active layer 3° p-type cladding layer 4. An n-type current limiting layer 5 is grown, and zinc is diffused until it reaches the crystal surface: the p-type cladding layer 4, thereby forming striped diffusion regions 6.

After that, a p-type ohmic electrode metal film 7 is formed on the entire surface of the grown crystal.
is attached, and a metal film 8 for an n-side ohmic electrode is attached to the substrate side.

Figure 1 (bl is an XX cross-sectional view of the laser in Figure 1 (al) viewed from the side in a direction perpendicular to the stripe; the light is reflected many times at the end face 9 and amplified; End face 9
It is emitted from.

In this semiconductor laser, as the operating time becomes longer, an oxide film containing non-radiative recombination centers grows on the end face 9 where light is reflected and transmitted, and as a result, the operating current of the semiconductor laser increases and the life span is shortened. It is known to be shorter. It is thought that such end face deterioration occurs due to the application of an electric field, temperature rise due to reabsorption of light, or oxidation due to contact with outside air.

As a countermeasure against this problem, there is a conventional method of forming a thin film of an insulator transparent to transmitted light on the end face. Since the formed thin film isolates the end face from the outside air, the end face is less susceptible to deterioration due to oxidation, and this thin film also serves to dissipate heat generated at the end face. Furthermore, when such a thin film is formed on the end facet of a semiconductor laser, by precisely controlling the thickness, it is possible to freely change the reflectance of the end face by taking advantage of the thin film's seven-wavelength property of light. It also has the advantage of being able to do a lot of things.

Conventionally, materials such as SiO2 and Ar203 have been used as materials for such thin films, but the present invention uses boron nitride (BN) instead of these materials. The formation method is, for example, CVD method (Chemical
It is formed by vapor deposition. Boron nitride has a thermal conductivity of 8.
102 (the thermal conductivity of boron nitride is 0)
．． BW/C7n·K) is the most advantageous material for effectively dissipating the heat generated at the end face.

An example in which a thin film is formed using boron nitride in a GaAs-Ga, -xAexAs semiconductor laser will be shown below with reference to FIG.

The first n-type 0.65ApO, 55As cladding layer 11 was formed with a thickness of 4 μm on the n-type substrate 10 (100) surface by liquid phase epitaxial method, and the second layer non-doped GaO was formed with 95kp.
o, as As active layer 12 of 0.2 μm, third layer p-type G? A fourth successive Lf1.45''[1,35As cladding layer 13 is grown to a thickness of 2 μm (FIG. 2(a)).

Next, a Si3N4 film 16 is applied to the surface of the grown crystal, and a width of 4 μm is applied.
m stripe-like windows are formed, selective diffusion is performed through these windows, and the diffusion surface becomes the third layer p-type GaO, 65Af0.
35AS cladding layer 13 (Fig. 2 (
b)).

Thereafter, the Si 3N a film 15 on the surface is removed, a metal for the p-side electrode is deposited, and an alloying process is performed to form the p-side ohmic electrode 16. A metal for the n-side electrode is deposited on the substrate side and alloyed to form the n-side ohmic electrode 17 (FIG. 2(C)).

After the semiconductor wafer thus produced is cleaved, a nitride film 18 is formed on the mirror-finished end surface to a thickness of 1800 mm by the CVN method (FIG. 2(d)). This nitriding method is used to grow a boron film using 6 tB2H as the material.
Growth was performed on the end face at 430° C. using NH 6 and 6 NH 3 . Thereafter, this laser chip is mounted on a Si block to complete the process.

In this way, the optical semiconductor device of the present invention is made of boron nitride.
By attaching this film to the end face as a protective film etc., the heat generated at the end face can be effectively dissipated and the life of the laser can be extended compared to when using the conventional 8102 film, which has industrial utility value. is high.

[Brief explanation of drawings]

Figure 1 (at is a cross-sectional view taken perpendicular to the stripe of a conventional planar stripe type laser;
Figure 1 (a) No.X-X sectional view, Figure 2 (a) to (d)
1A and 1B are cross-sectional views of each manufacturing process of an optical semiconductor device in an embodiment of the present invention. 1-n lj, lj GaAs substrate, 2...
N-type "a + xkexAs cladding layer, 3...
・Non-doped Ga, A/yAs active layer, 4...
p-type Ga, -xA I! X As cladding layer, 6...
... n-type GaAs current limiting layer, 6 ... zinc diffusion region, 7 ... metal film for p-side ohmic electrode,
8...Metal film for n-side ohmic electrode, 9...
...Laser chip end face, 10-=-n-type GaAs substrate,
11-- n-type Ga1-xApxAs cladding layer, 12
--- Non-doped Ga + yA p y S active layer, 13 -- p-type Ga, -xA/xAs cladding layer, 1
4...n-type GaAs current limiting layer, 15...
513N4 film, 16...metal film for p-side ohmic electrode, 17...metal film for n-side ohmic electrode, 1,8...BN end face protection film, 19...・Zinc diffusion area. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure ((1) (b) q Figure 2

Claims (1)

[Claims] An optical semiconductor device characterized in that a film made of boron nitride is formed on a crystal surface through which light is transmitted or reflected.