JPS60214578A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To provide a highly efficient and reliable high-power device furnished with an excellent reflection film structure capable of withstanding heavy duties by a method wherein one of the reflecting surfaces of an oscillator is coated with a first metal film which is further coated with a second metal film whose reflectivity is higher than that of the first metal film. CONSTITUTION:A first metal film 20 is a Ti film typically 100Angstrom thick formed on a dielectric film 19 by means of evaporation or sputtering. A second metal film 21 is formed, which is a 0.1-0.2mum-thick Au film attached to the first metal film 20. The first metal film 20 functions only to augment adhesion between the second metal film 21 and the dielectric film 19, and is composed of Ti, Ni, Cr, Mo, or W, with its thickness thin enough to cause but a sufficiently small optical loss. The second metal film 21 is the reflecting film, and is built of such a high-reflectivity metal as Al, Au, Ag, Cu, Pt, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a semiconductor light emitting device, and particularly to a semiconductor light emitting device comprising a metal film with high reflectance and good stability as one reflecting mirror surface of a resonator.

(b) Technical Background Optical communication systems, which serve as a medium for information signals, continue to make remarkable progress as a major pillar of the information society. Semiconductor light emitting devices are the most important component in systems that use light as a medium, such as optical communications. Improvements in fundamental characteristics such as mode oscillation, improved quantum efficiency, improved linearity of current-source characteristics, and increased output are contributing to the advancement of systems.

(C1 Conventional technology and problems) In a semiconductor light emitting device, a laser is provided with an optical resonator in order to amplify the original light by stimulated emission. ta fapley
The Perot shape is often used.

Conventionally, for the purpose of extending the life of a conductor laser and improving its efficiency, a thin film has been provided on the end face of the resonator.

For example, gallium arsenic (-) has a refractive index of n×3.6.

Gallium aluminum Φ arsenic (Gas −x At
Silicon dioxide (S
in, ) (1 = -1,45) + dielectric film such as aluminum 1112 (At203) (n = 1.65), silicon VII (diaNn) (n = 1.95),
If the thickness is set as an integer multiple of the half-length, if no film is provided, a reflectance of approximately 31 inches, which is equal to 1, can be maintained and the effect of protecting the crystal end face can be obtained. If it is multiplied by an odd number, the protective film will have an extremely low reflectance.

On the other hand, as a film structure that increases the reflectance of the end face, for example, 8i0! and 5iaN4 films with different refractive index l/
A structure in which layers are alternately laminated with a thickness of four wavelengths is known. If the laser beam needs to be emitted only in one direction of the resonator, it is possible to increase the efficiency by providing a reflective film on the other end face. Desirably, a metal film has conventionally been used as the reflective film in this case. FIG. 1 is a cross-sectional view showing one example, in which 1 is a semiconductor substrate, 2 and 3 are electrodes, 4 and 5 are dielectric films, and 6 is a metal film, and the laser source is a dielectric M411.
It is radiated from the end face of 11.

In order to obtain a high reflectance, the metal film 6 is made of a pot (Au).
), aluminum (At), platinum (Pl) + 98
(Ag).

Copper (Cu) or the like is used. The dielectric film 5 is provided to insulate the conductor film 6 from the semiconductor substrate l and to compensate for the original phase shift caused by reflection from the conductor surface, and its thickness is l/4. The wavelength or an odd multiple thereof. Note that the dielectric film 4 is provided as in the example described above depending on the purpose.

However, recently, the necessity of increasing the output of conductor lasers and unifying the mode has been increasing in many fields of optoelectronics. For this purpose, the cross-sectional dimensions of the active region are, for example, 2.0 to 4.0 μm wide and 0.0 μm thick.
It is limited to about 0.05 to 0.2μ bait. This condition means that the end face of the resonator bears a power of about IOMW/-.

The conventional metal reflective film as shown in FIG. The adhesion strength between the metal film 6 and the metal film 6 is a non-light component, and if a power of several tens of mW or 1OMW/aA or more is applied as described above, destruction such as peeling of the metal film 6 will progress and the metal film 6 will rapidly deteriorate.

Examples of metal materials that can form a film with excellent adhesion to the electric film include titanium (T) and chromium (Cr).
, nickel (Ni), molybdenum (MO), tungsten (W), etc. are known.

However, these metals have high original absorption (for example, if the reflective film is formed of Ti, the reflectance will be about 60 cm, which is a noticeable drop in efficiency compared to about 90 cm for Au). The power increase of semiconductor lasers is restricted.

(d) Purpose of the Invention The present invention addresses the above-mentioned situation and provides a reflective film structure that has excellent reflectance and can withstand a large power load, and provides high output with high efficiency and reliability. The object of the present invention is to provide a semiconductor laser.

tel Structure of the Invention The object of the present invention is to provide a second metal film on one reflective surface of the resonator via a first metal film, and the second metal film is in contact with the first metal film. This can be achieved by using a semiconductor light emitting device made of a material with higher reflectance.

The first gold M7X film is a film interposed to increase adhesion to a dielectric film, etc., and is made of, for example, titanium (T').
) r-'-t/yru (Ni), rim (Cr),
It is made of molybdenum (Mo) or tungsten (W), and its thickness is kept within a range where the original loss is sufficiently small.

The metal film 42 above is an original reflective film, and is made of a metal that can provide a high reflectance, such as aluminum (Az), gold (Au), silver (Ag), copper (Cu), or platinum (Pt).
Formed by etc.

(fl　Embodiments of the invention The present invention will be specifically explained below using examples.

FIG. 2 is a cross-sectional view taken through the center of the resonator according to the embodiment of the present invention. In the figure, 11 is an n[GaAs substrate, 12 is an n@Ga t -y Aly k@ confinement layer, 13 is a p m Oa ]-X layer AS active layer,
14 is a pm Ga r -y A-ty As confinement layer, 15 is a p GaAs layer, 16 is a p-side electrode, 17 is an n-side electrode, 18 and 19 are dielectric films, 20 is the first metal film, 21 is the second metal film.

In this example, after the n14il electrode 17 is made of gold/germanium/gold (AuGe/Au) and the p-side electrode 16 is made of titanium/platinum (Ti/Pz), the semiconductor substrate is divided into a crystalline array. It is made into a rod shape, and the resonator end face is formed by forming folds.

Next, in this embodiment, dielectric films 18 and 19 are formed using AtzOa. The thickness of the dielectric film 18 is set to λ/4n, λ/2n (n is the refractive index of the dielectric film), etc. according to conventional techniques. Also, the thickness of the dielectric film 19 is λ/4
n sj, that is, about 1200X for λ-52ooX1
It is said that

On the dielectric film 19, a metal TI is deposited to a thickness of, for example, toox, by, for example, vapor deposition or sputtering to form the first metal film 20, and then Au is deposited to a thickness of, for example, 01 to 0.2 μm.
After that, the arrayed elements are divided into individual chips and assembled. Light is emitted through the dielectric film 18.

In the structure of the present invention such as the embodiments described above, the first metal film 20 made of Ti or the like, which has a large absorption coefficient and therefore a large loss, is sufficiently thin compared to the wavelength of light. The loss is extremely small (the loss of light is determined by the second metal 21 made of Au or the like having a small absorption coefficient).

Therefore, the reflective film base constituted by the two-layer metal film according to the present invention provides a reflectance that is approximately equal to the reflectance obtained by only the second metal film. In the above example, a reflectance of about 90% was obtained, which is much higher than the reflectance of about 60% in the case of only T-bond (approximately the reflectance of about 95% in the case of only Au). It was confirmed that they are equal.

Furthermore, regarding this example and a comparative sample formed directly on the At20a film on A u g 1, the thickness of 40 m
W constant output constant output property, current increase rate is 2 in comparison sample
) <tO"-'/H and showed a tendency to further increase over 1,000 hours, whereas in this example, the current increase rate was 7. There was no change, and the effect of the present invention was confirmed.

In the above embodiment, the first metal film has a thickness of approximately 1 mm.
00X Ti film is provided, but the metal material is Ti.
For example, without limitation, N 1 , Cr, MO+W
etc., and the optimum thickness is selected according to the materials of both metal films and the operating conditions of the laser. Also the second
The selection of the material, thickness, etc. of the metal film is the same as that of the conventional metal reflective film.

Furthermore, in the embodiments described above, either the dielectric film 19 is provided on the end surface of the semiconductor substrate and the first metal film 2° is formed thereon, or the dielectric film 19 is not provided and the vicinity of the end surface of the semiconductor substrate is formed. A structure in which the first and second metal films are directly formed with high resistance is also possible.

(g) As described in detail, according to the present invention, in a semiconductor laser in which one reflecting mirror surface of a resonator is formed of a metal film, it is possible to provide a metal film having a high reflectance firmly and with good stability. Therefore, it is possible to realize a high-power semiconductor laser with high efficiency and reliability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional example of a semiconductor laser having a metal reflective surface, and FIG. 2 is a sectional view showing an embodiment of the present invention. In the figure, 11 is an n fil GaAs substrate, 12 is an n-type GaAtAs layer, 13 is a GaAzAs active layer, and 14 is an n-fil GaAs substrate.
is I) fil Ga AtAs layer, 15 is I) ff
The iGaAs layer, 16 and 17 are electrodes, 18 and 19 are dielectric films, and 20 and 21 are metal films.

Claims (3)

[Claims] (1) A second gold M4 antinode is provided on one reflective surface of the resonator via a first metal film, and the second metal film is made of a material having a higher reflectance than the first metal film. A semiconductor light emitting device characterized by: (2) The semiconductor light emitting device according to claim 1, wherein the first metal film is formed of titanium, nickel, chromium, molybdenum, or tungsten. (3) The second metal film is made of aluminum, gold 1fs
+ The semiconductor light emitting device according to claim 1 or 2, characterized in that it is formed of copper or platinum.