JPS62155574A - Light emitting diode - Google Patents

Abstract

PURPOSE:To obtain a large output coupled to fiber and prevent decrease of light output due to the conduction of a current, by forming a silicon nitride film on the side surface of a circular mesa structure of a light emitting diode wherein the circular mesa structure containing a double hetero lamination structure having an active layer is arranged on a semiconductor substrate. CONSTITUTION:An n-type InP clad layer 12, an n-type InGaAsP active layer 13, a p-type InP clad layer 14 and a p-type InGaAsP contact layer 18 are formed in order on an n-type InP substrate 11 by, for example, a liquid phase epitaxial method. Subse quently, a groove 15 is formed by, for example, chemical etching applying Br methanol, the groove of which is in the form of a ring having an internal radius of 25mum and penetrates the active layer. The inside of the groove is a circular mesa which acts as a luminous part. A silicon nitride film 21 is formed except the surface of the inner contact layer 18, on the surface of which a TiPt film is formed to constitute a p-type electrode 16. After polishing the substrate 11, an AuGeNi film is formed to constitute an n-type electrode 19 except a light taking out window 17 being a concentric circle of the groove 15, and finally a gold plating layer 20 is formed on the p-type electrode 16. The light output variation with time caused by flowing a current, at for examaple 150 deg.C, exhibits no initial decrease as shown in the figure, and the operation is stabi lized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor light emitting diode (hereinafter referred to as LED) suitable for optical fiber communication.

(Prior Art and its Problems) For LEDs intended for optical fiber communication, it is important that they have high brightness, a large fiber-coupled output, and high reliability. Based on the research results of the present inventors, we obtained a remarkable improvement in the fiber-coupled output by using an LED whose light emitting part has a circular mesa structure.
8 (1984) P, 15-F, 20).

However, this circular mesa structure LED has a problem in that the optical output decreases by 10 to 20% at the initial stage of energization, then stabilizes, and the initial output may not be maintained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a highly reliable LED that has high fiber-coupled output and significantly reduces the decrease in optical output due to energization.

(Means for Solving the Problems) Means provided by the present invention to solve the above-mentioned problems is a light emitting diode having a circular mesa structure including a double-hetero stacked structure having an active layer on a semiconductor substrate. ,
A feature is that a silicon nitride film is formed on the side surface of this circular mesa structure.

(Operation and Principle of the Invention) From the experimental results of the present inventors, it has been found that the decrease in output at the initial stage of energization, which has conventionally been observed, is due to the decrease in luminous efficiency on the side surface of the circular mesa structure. It was found that this was because the silicon oxide film that had been completely formed was not suitable as a protective insulating film. That is, it is thought that this is because Ga, which is the host element of the semiconductor, diffuses into the silicon oxide film, causing defects near the semiconductor surface and reducing the luminous efficiency.

According to experiments conducted by the present inventors, the silicon nitride film is made of Ga.
It was found that this film has a remarkable effect as a protective insulating film to prevent the diffusion of

(Example) Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention.

In the structure of this embodiment, an n-type InP cladding yf! is formed on an n-type InP substrate 11. j12, n-type nGaAsP
Active layer 13, p-type InP cladding layer 14, p-type InGa
The AsP contact layer 18 is sequentially formed by, for example, a liquid phase epitaxial method. Subsequently, by chemical etching using, for example, Br-methanol, a ring-shaped groove 15 having an inner diameter of about 25 cm and penetrating the active layer is formed. The inside of the groove 15 is a circular mesa region that becomes a light emitting part. p-type InGa inside groove 15
A silicon nitride film 21 is formed except on the surface of the AsP contact layer 18, and I, P is formed on the surface of the p-type contact layer 18.
.

A film is formed to form an n-type electrode 16. After polishing the n-type InP substrate 11 to a thickness of about 1100Pr, the annular groove 15 is concentrically formed except for the light extraction window 17 with a diameter of about 100P, and other parts are A.
A uGeNi film is formed to form an n-type electrode 19. Finally, gold plating W with a thickness of 10~20ρ on the n-type electrode 16! Form 20. FIG. 2 is a diagram showing a change over time in the optical output of the embodiment of FIG. 1 due to energization at a temperature of 150°. As is clear from the figure, this example operated extremely stably without any decrease in optical output at the initial stage of energization.

(Effects of the Invention) As explained in detail below, according to the present invention, it was possible to obtain a highly reliable LED that has a high fiber-coupled optical output and significantly reduces the decrease in optical output due to energization.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG.
FIG. 3 is a characteristic diagram showing a change in optical output over time in the illustrated embodiment. In the figure, 13 indicates an active layer, and 21 indicates a silicon nitride film.

Claims (1)

[Claims] 1. A light emitting diode comprising a circular mesa structure including a double-hetero laminated structure having an active layer on a semiconductor substrate, characterized in that a silicon nitride film is formed on a side surface of the circular mesa structure.