JPH0770758B2 - Light emitting semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting semiconductor device, and more particularly to a light emitting semiconductor device having a high performance by arranging a spherical lens on the surface portion of a solid state light emitting element.

Configuration of conventional example and its problems Optical communication technology has reached the stage of practical use, and a high-performance light emitting element is strongly demanded.

In general, a light emitting element for optical communication is configured so that a light emitting region is narrowed to a small area and a high density light emitting output is obtained in order to improve the coupling property with an optical fiber.

FIG. 1 is a cross-sectional structural view of a typical conventional example of a light emitting device for optical communication. The light emitting portion has a double hetero structure having a junction region for current constriction, and a spherical lens is arranged in front of the light emitting portion. . That is, this light emitting device comprises an n-type gallium arsenide (hereinafter abbreviated as GaAs) substrate 1, an n-type gallium aluminum arsenide (hereinafter abbreviated as GaAlAs) layer 2, and a P-type
GaAs layer 3, P-type GaAlAs layer 4 and n-type GaAlAs layer 5
Are sequentially formed by an epitaxial growth technique, and further,
An opening with a diameter of about 100 μm is formed in a part of the n-type GaAlAs layer 5 to form a light emitting window, and then a high concentration P-type (P ⁺ ) layer 6 is provided on the entire surface by diffusion and introduction of zinc (Zn). It has a so-called double hetero structure in which ohmic electrodes 7 and 8 are formed on both surfaces, and a microsphere lens 9 having a diameter of several hundreds of μm is bonded to the light emitting window with a transparent epoxy resin 10.

In this structure, the n-type GaAlAs layer 5 is referred to as a current confinement junction region, and the current flowing from the electrode 7 is mostly concentrated in the area of the opening, so that the emission output portion is also almost in the area of the opening. To obtain a high-density light emission output.
The light emitting region is the P-type GaAs layer 3, and the P-type GaAlAs layer 4 and the n-type GaAlAs layer 2 on both sides thereof are respectively
It is called a confinement layer and is a region for confining minority carriers.

However, according to the above-mentioned conventional example, when the spherical lens 9 is adhered, there is a problem that the light emission output is influenced by the shape of the light emission window.

An object of the present invention is to provide a light emitting semiconductor device capable of realizing stable and high output performance by optimizing the shape of a light emitting window.

According to the present invention, the diameter of the current confinement junction region on the solid surface side is 80 μm.
m recesses are formed, and the peripheral side surface of the recesses is in the range of 40 to 50 degrees from the vertical direction of the solid surface, and has an upward slope from the bottom of the recesses. Due to the electrode layer formed on the periphery, the diameter of the light emitting plane is 120μ.
m light emitting window is formed, is in contact with the light emitting plane, and has a diameter of
This is a light-emitting semiconductor device characterized in that a ball lens of 500 μm is provided. With this, it is possible to increase the light emission output and optimize the coupling with the optical fiber.

Description of Embodiments Hereinafter, the present invention will be described in detail by way of embodiments with reference to the cross-sectional view of FIG.

The structure of the light emitting element, in particular, each layer including the light emitting region is generally the same as that of the conventional example of FIG. 1, but is manufactured according to the following procedure.

First, n-type GaAs substrate 1 is a silicon (Si) doped, used as a carrier concentration of 1 × 10 ¹⁸ cm ^-3, on the sequentially formed by continuous epitaxial growth techniques double heterostructure. The growth condition is that the growth start temperature is
The temperature is 820 ° C, the growth stop temperature is 790 ° C, and the cooling rate during this period is set to 0.1 ° C / min to 1 ° C / min. Among the respective layers, the aluminum arsenide (AlAs) mixed crystal ratio (X) in the GaAlAs layer is such that the n-type GaAlAs layer 2 has X = 0.25, and the P-type GaAl
The As layer 4 had X = 0.35, and the n-type GaAlAs layer 5 in the junction region for current confinement was set to X = 0.15 in consideration of the emission absorption and the contact with the electrode 7. The thickness and carrier concentration of each growth layer are as follows.

n-type GaAlAs layer 2 ...... 20 μm, 2 × 10 ¹⁸ cm ^-3 P-type GaAs layer 3 ・ ・ ・ 0.8 μm, 5 × 10 ¹⁷ cm ^-3 P-type GaAlAs layer 4 …… 3 μm, 2 × 10 ¹⁷ cm ^-3 n GaAlAs layer 5 ... 4 μm, 1 × 10 ¹⁸ cm ^-3 Note that tin (Sn) is used as the n-type impurity and germanium (Ge) is used as the P-type impurity, and the emission output obtained by this is the peak. The wavelength is 880 nm.

Next, an etching recess having a diameter of 80 μm and a depth of 30 μm is formed in the n-type GaAlAs layer 5 by a photolithography technique. As this etching solution, a mixed solution of hydrogen peroxide (H ₂ O ₂ ) and nitric acid (NH ₃ ) is used. By changing the composition of the etching solution, the taper angle φ of the recess as shown in FIG. 2 can be changed. Experience has shown that the emission output and the emission intensity characteristic thereof are slightly changed depending on the taper angle φ.
The following table shows etchant composition, taper angle φ, forward current
Shows the emission output (mW) and emission half angle on the light emitting intensity distribution characteristics in the I _F = 100 mA.

The half emission angle represents the angular width at which the maximum intensity on the central axis of the emission intensity distribution is 1, and the smaller the angle, the sharper the directivity. There is.

Considering the coupling property with an optical fiber, the light emitting element for optical communication is limited to a half emission angle of 10 degrees or less. Therefore, in view of the characteristics in the above table, the taper angle φ is limited to 40 ° to 50 ° at the most, and beyond this, the directivity becomes dull and it becomes unsuitable for optical communication. Nevertheless, it can be seen that if the taper angle φ is set to 40 to 50 degrees, the light emission output will definitely be improved by 20% or more.

The method of forming the P ⁺ layer 6 may be performed by using, for example, a diffusion source
A diffusion layer having a depth of 1.5 μm can be obtained by diffusion treatment using zinc arsenide (Zn ₃ As ₂ ) in a sealed quartz tube at 650 ° C. for 30 minutes. In addition, the electrode layer 7 formed thereon is formed around the etched recess, so that the diameter of the electrode layer 7 is 12 mm around the recess.
A 0 μm emission window was provided, and this portion was made to be the emission surface. Further, a minute glass ball lens 9 having a diameter of 500 μm is adhered and fixed on the light emitting surface with a transparent epoxy resin 10. In this case, the glass ball lens 9 has a refractive index of 1.91.
It is formed by using a high-refractive-index glass.

EFFECTS OF THE INVENTION According to the present invention, since the aperture shape of the light emitting window portion on the solid surface side is a funnel shape with a peripheral end surface inclination, a reliable increase in light emission output is achieved, and a light emitting device for optical communication, especially Thus, it is possible to realize a light emitting semiconductor device having a good coupling property with an optical fiber.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional light emitting device, and FIG. 2 is a sectional view of a light emitting semiconductor device according to an embodiment of the present invention. 1 ... n-type GaAs substrate, 2 ... n-type GaAlAs layer, 3 ... P-type
GaAs layer, 4 ... P-type GaAlAs layer, 6 ... P ⁺ layer, 7,8 ... Ohmic electrode, 9 ... Spherical lens.

Claims (1)

[Claims] 1. A diameter of 80 in the current confinement junction region on the solid surface side.
A μm recess is formed, and the peripheral side surface of the recess is in the range of 40 ° to 50 ° from the vertical direction of the solid surface, and has an inclination that spreads upward from the bottom of the recess. Due to the electrode layer formed on the periphery, the diameter looking into the light emitting plane is 120
A light emitting semiconductor device, wherein a light emitting window of μm is formed, and a spherical lens having a diameter of 500 μm is disposed in contact with the light emitting plane.