JPH08236861A - Semiconductor laser element - Google Patents

Abstract

PURPOSE: To obtain the passivation method of a reflecting surface of semiconductor laser which is excellent in workability and mass-productivity, by forming a dielectric film from the side surfaces of a plurality of semiconductor layers containing an active layer laminated on a semiconductor substrate to the side surface of the semiconductor substrate, and forming a region in which the dielectric film is not formed, on the semiconductor substrate side surface. CONSTITUTION: On the surface of an N-type GaAs substrate 1, a belt type recessed trench is formed, on which an N-type GaAlAs clad layer 3, a GaAlAs active layer 4, a P-type GaAlAs clad layer 5 and an N-type GaAs cap layer 6 are formed. After that, a P side electrode 8 is formed. A photoresist film is used as a mask, and a resonator reflecting surface 11 is formed by a reactive ion beam etching method. The reflecting surface can be formed almost vertically. By using a sputter coating method, SiO2 10 is formed on the whole surface. In this case, SiO2 creeps over the resonator reflecting surface, and a passivation film is formed. A photoresist mask is formed, SiO2 on the P side electrode is eliminated, and an N side electrode is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection surface passivation treatment method for semiconductor laser devices, which is suitable for mass production and integration with electronic circuits.

[0002]

2. Description of the Related Art A semiconductor laser device has advantages such as a small size, high efficiency, and low power consumption which are not found in other lasers, and has been widely applied to optical communication light sources, optical disk pickups, and the like. Came. One of the reasons why the semiconductor laser has been rapidly put into practical use is that the reflection surface of the semiconductor laser resonator is passivated with a dielectric material or the like to remarkably improve the deterioration phenomenon of the laser element due to the end surface deterioration. Can be mentioned. There are numerous examples of reflective surface passivation treatments (see, for example, K. Kressel et al., AR C. Review, Vol. 36, No. 2, No.
230 pages, 1975 (K.Kressel et al., RCA Review Vol.36,
No.2, P.230,1975) and F.R.Nash et al., Applied Physics Letters Vol. 35, No. 12, 905, 1979.
Year (FRNash et al. Appl. Phys. Lett. Vol.35No.12,
P.905,1979)).

However, the conventional reflecting surface for a resonator of a semiconductor laser is formed by a cleavage plane utilizing a specific crystal orientation. Therefore, the passivation process such as coating of the dielectric film on the reflecting surface for improving the reliability of the laser has been performed after the cleaved chip state or after bonding to the stem or the like. Therefore, the above-mentioned laser reflection surface passivation treatment has a very poor workability and a large problem of poor mass productivity.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser reflecting surface passivation method which solves the above problems and is excellent in workability and mass productivity.

[0005]

In order to achieve the above object, in the present invention, passivation treatment of a laser reflecting surface is performed by the following method.

First, the laser double hetero layer is processed almost vertically by, for example, a chemical etching method or a dry etching method to form a laser reflecting surface. Next, a dielectric film for passivation is formed on the entire surface in the wafer state as it is. As the dielectric film for passivation, an example of SiO ₂ is shown in the following embodiments, but it goes without saying that another known dielectric film may be used. At this time, passivation of the reflection surface is performed by wrapping the dielectric film around the concave portion forming the reflection surface. Next, using photolithography, the dielectric film on the surface electrode and the like is removed to expose the electrode surface.

[0007]

According to the present invention, the laser reflection surface can be passivated in a wafer state, so that workability and mass productivity are remarkably improved as compared with the conventional method in a chip state.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 shows a channeled embodiment of the present invention.
Substrate Planar (CSP for short) structure GaAS-GaAlAs semiconductor laser cross-sectional view (a) in the light traveling direction, and
It is a vertical cross-sectional view (b). Explaining each part, 1
Is an n-type GaAs substrate (Si-doped, ~ 1 x 10 ¹⁸ cm ^-3 , (100)
Surface), a band-shaped groove 2 having a width of about 5 μm and a depth of about 1.3 μm is formed on the surface of the substrate, and an n-type Ga _0.6 Al _0.4 As clad layer 3 (Te-doped, n-1 × 10 ¹⁸ cm ^{− 3} , thickness outside the groove about
0.3 μm) 4, Ga _0.86 Al _0.14 As active layer 4 (undoped,
0.06 μm), p-type Ga _0.6 Al _0.4 As cladding layer 5 (Zn-doped, p-5 × 10 ¹⁷ cm ⁻³ , thickness about 2 μm) n-type GaAs cap layer 6 (Te-doped, n-1 × 10 ¹⁸⁾ cm ^-3 , thickness about 0.5μ
m) is formed. Reference numeral 7 is a region inverted to p-type by Zn diffusion, and has a structure in which a current efficiently concentrates in the active region through this portion. The passivation film 10 of the present invention is formed on the resonator reflection surface. In this embodiment, the passivation film 10 is a SiO ₂ film formed by a sputter coating method and has a thickness of about 230 nm. Next, the features of the present invention will be described with reference to FIG. FIG. 2 shows a method for manufacturing the device of the embodiment of the present invention shown in FIG.
In a semiconductor laser device manufacturing process, after stacking each semiconductor layer on a semiconductor substrate, a p-side electrode 8 is formed, and a resonator reflection surface 11 is formed by a reactive ion beam etching method using a photoresist film as a mask ( FIG. 2A). Chlorine Cl ₂ is used as an etching gas, the pressure is about 1 × 10 ^-1 Pa,
Etching was performed at an acceleration voltage of 400V. The etching depth is about 7 μm. The angle of the reflecting surface could be made almost vertical. Next, by the sputter coating method,
SiO ₂ 10 was formed on the entire surface (FIG. 2B). At this time, SiO ₂ also wraps around on the resonator reflection surface, and a passivation film is formed at a rate of about 60% with respect to the flat surface portion. The passivation film thickness on the reflecting surface was about 230 nm. As a method of sputter coating, the target is SiO ₂
Was performed by a high frequency sputtering method in an Ar atmosphere. The feature of sputter coating is that a dielectric film can be formed inside the groove as described above. Next, a photoresist mask was formed by photolithography, and SiO ₂ on the p electrode was removed by etching. A mixed solution of hydrofluoric acid and ammonium fluoride was used as the etchant. Continued to,
The back surface was polished and etched to have a wafer thickness of about 250 μm, and then an n-side electrode was formed (FIG. 2C).

This semiconductor laser oscillated in a transverse fundamental mode with a threshold current value of about 50 mA and an oscillation wavelength of about 780 nm and an optical output of about 10 mW. As described in the present embodiment, since the passivation treatment of the semiconductor laser reflecting surface is performed at the wafer stage, the manufacturing process is remarkably simplified as compared with the conventional method in the chip state.

As described above, according to the present invention, the passivation process of the semiconductor laser reflecting surface can be performed before dividing into chips, and the manufacturing process of the semiconductor laser device is remarkably improved. The present invention can be applied not only to the GaAlAs system, but also to other materials, optical integrated devices, optical / electronic integrated devices, and the like.

[0012]

As described above, the present invention provides a method of performing passivation on the reflecting surface of a semiconductor laser in a wafer state and removing an unnecessary dielectric film on the electrode surface or the like. Compared to the method of performing passivation treatment in a chip state or the like, the device manufacturing process has been significantly improved, and a manufacturing process suitable for mass productivity has become possible. Also,
The present invention can be applied to an optical integrated device or an optical / electronic integrated device in which a laser and an electronic circuit are integrated, and its practical effect is great.

[Brief description of drawings]

FIG. 1A is a sectional view parallel to a light traveling direction of a semiconductor laser showing an embodiment of the present invention, and FIG. 1B is a sectional view in a vertical direction thereof.

FIG. 2 is a cross-sectional view showing a process of manufacturing a semiconductor laser device according to the present invention.

[Explanation of symbols]

1 ... n-GaAs substrate, 3 ... n-Ga _0.6 Al _0.4 As clad layer, 4 ...
Ga _0.86 Al _0.14 As active layer, 5 ... p-Ga _0.6 Al _0.4 As clad layer, 10 ... Reflective surface SiO ₂ passivation film, 11 ... Laser reflective surface.

Claims (1)

[Claims] 1. A semiconductor laser device comprising a semiconductor substrate, a plurality of semiconductor layers including an active layer laminated on the semiconductor substrate, and an electrode formed on an upper surface of the semiconductor layer, wherein a side surface of the semiconductor layer is provided. A semiconductor laser device, wherein a film made of a dielectric is formed on a side surface of the semiconductor substrate, and a side surface of the semiconductor substrate has a region where the dielectric is not formed.