JPS5840872A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To make external quantum efficiency extremely large by forming the light extracting region of the semiconductor light-emitting devices in stepped shape of which a corner section is rounded. CONSTITUTION:N And P epitaxial layers 2, 3 are grown continuously onto an N type GaP substrate 1, electrodes 5, 6 are attached, and a section up to a P-N junction 4 from the surface of the layer 3 is diced to shape form of which similar polygons are stacked and approximately finished in semispherical shape. The corners of stages are removed through chemical etching, and said section is brought close to a semisphere. The whole is separated into the light-emitting devices. When the P-N junction 4 is conducted in the forward direction, light emitted from the P layer passes through the semispherical layer 3 and is extracted to the surface. Since light components exceeding a critical angle are few in a spherical surface and light is hardly reflected at the inside at that time, the external quantum efficiency is improved remarkably, and brought to approximately treble or higher of a plane type.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a light-emitting element using a compound semiconductor, and is effective when a light-emitting portion is provided over the entire surface of one side by a liquid phase growth method or the like.

Conventionally, the light-emitting surface structure of a light-emitting element is a flat structure regardless of whether it is a selective diffusion wall type or a full-emission type, so that the majority of the light source is located at a certain depth parallel to the surface from which light is extracted. It is known that the component of light that exceeds the critical angle toward the interface is internally reflected and absorbed inside the crystal, or that there is absorption of a luminescent component corresponding to the length of the luminescent optical path that travels within the crystal at the above depth. ing.

FIG. 1 is a cross-sectional view of a conventional full-surface light-emitting device manufactured by forming a P-type GaP crystal layer on an N-type GaP crystal material. First, the Nffl GaP substrate 1.
Second, an N-type GaP layer 2 and a P-type GaP layer 3 are successively epitaxially formed by a known liquid phase growth method to form a PN junction 4. Next, a coating electrode 5 is formed on a part of the P side of the PN junction 4, and the GaP substrate i ill! A back electrode 6 is formed on the + side, and a known dicing process is then carried out to produce individual light emitting elements.

When current is applied in the forward direction to the N-junction 4 of the light emitting device having the structure shown below, I'IQI 1j (light is emitted from the region j, and this light travels to the back and side surfaces as well as light 7 that travels to the front surface.
is obtained. (In the following description, since the present invention relates to light traveling toward the front surface, light traveling toward the back surface and side surfaces will be omitted.)

The light traveling to the interface is divided into a component that is internally reflected at the surface of the P-type ()aP layer 3 and a component that passes through the surface while being internally absorbed. In principle, it is impossible to completely eliminate these internal reflections and internal absorptions when the light emitting section has a planar structure due to the manufacturing method.

As a measure to solve the above-mentioned disadvantages, it has been theoretically and experimentally proven that internal reflection and internal absorption can be minimized by processing the light extraction side surface into a curved surface, ideally into a hemispherical shape. However, many problems remain that make it impractical in terms of production costs and processing technology.

SUMMARY OF THE INVENTION An object of the present invention is to significantly improve the above-mentioned drawbacks, to form a hemispherical light emitting section which has been difficult to realize, albeit approximately, and to provide a semiconductor light emitting device with extremely high external quantum efficiency.

According to the present invention, it is a method that prevents loss of external quantum efficiency due to internal reflection and eliminates manufacturing and technical difficulties without causing deterioration of forward voltage characteristics or light emission characteristics due to current concentration.

Embodiment 11 of the present invention will be described in detail below with reference to the drawings. The first embodiment is similar to the conventional method, and is performed on a light emitting element formed by stacking Nl and PlGaP crystal layers on an N-type GaP crystal material. FIG. 2 is a diagram showing the optical path of light emitted from the light emitting device and the light emitting part obtained by the method of the present invention. As in the conventional method, first, an N-type GaP substrate 1 is coated with an N-type 032 layer 2.
and P-type GaP layer 3 are successively epitaxially formed by a known liquid phase growth method to form a PN junction 4. Furthermore, a surface electrode 5 is formed on a part of the P side of the 1'N junction 4, and the G
A back electrode 6 is formed on the aI′ substrate 1 side. Next, PIjl
A polygonal protrusion surface is left by a plurality of known dicing operations in which the direction is changed using a blade having a wide width in the depth direction from the surface of the iGaP layer 3 to the PN junction 4, and the A similar polygonal protrusion larger than the protrusion is left by a plurality of dicing operations in different directions using a narrower blade than a wider blade. This operation is repeated one after another to form a shape that looks like a stack of polygonal prisms of similar shapes and is finished into an approximate hemispherical shape. Next, the corners of each step are etched using a known chemical etching method to further approximate the hemispherical shape. Thereafter, it is separated into each light emitting element by full width dicing or half dicing.

When current is applied in the forward direction to the PN junction 4 of the light-emitting element with the above structure, the light emitted from the P-type head region is approximately hemispherical P-type GaP
It passes through layer 3 and peeks out to the surface.

The process of passing through the GaP layer 3 is the same as the conventional method.

Although attenuation occurs due to light absorption, there are few components exceeding the critical angle on the spherical surface, and there is little internal reflection, so the external quantum efficiency is dramatically improved and is about three times or more compared to a planar view.

Next, a second embodiment will be described in which the present invention is applied to an infrared light-emitting element generally called an upside-down type in which the direction of the P-type head region Nu region is reversed.

FIG. 3 is a diagram showing light emission paths from an infrared light emitting device and a PN junction obtained in a second example according to the present invention.

First, a N I GaAs1d 9 and a P-type GaAs layer 10 are successively formed on an N-type GaAa substrate 8 by a liquid phase growth method to form a PN junction, that is, a light emitting section 4 . Light can be extracted from the N-type GaAs substrate 8 side of the light emitting element.

Turn the P side and N side upside down. Then PN junction 4O
A front electrode 11 is formed on a part of the N1GaAa substrate 8 on the N side, and a back electrode 5-12 is formed on the P-type GaAs layer 10 side. Thereafter, the N side of the PN junction is processed into an approximately hemispherical shape by a combination of the plurality of dicing operations and chemical etching according to the present invention.

When the PN junction 4 of the light emitting device with the above structure is energized in the forward direction, light is extracted from the N side, and the external quantum efficiency is
Similar effects can be obtained.

The same effect can be obtained by reversing the dicing operation a plurality of times as a process for finishing the approximate hemispherical trap and finishing sequentially from the lower part of the stepped shape. Father above.

It goes without saying that the same effect can be obtained by performing mesa etching multiple times instead of dicing multiple times, regardless of which side is finishing from the bottom.

Further, as an embodiment of the present invention, an example in which the light emitting region is formed by liquid phase epitaxy has been described, but similar effects can be obtained when the light emitting region is formed by vapor phase epitaxy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the conventional method, and FIG. 6- FIG. 3 is a sectional view of a light emitting device according to an embodiment of the present invention. FIG. 2 shows a GaP-based structure, and FIG. 3 shows a GaA-based upside-down structure. 1...N-type GaP substrate, 2...N-type O
a I' layer, 3...P-type GaP layer, 4...
...PN junction, 5...GaP, system surface electrode, 6.
...OaP-based back electrode, 7...Emission optical path, 8...N71 GaAs s substrate, 9...
...N-type GaAs layer, 10...P-type GaA
s layer, 11...GaAs-based surface electrode, 12...
. . . indicates a GaAs-based back electrode. Half 1N￥l

Claims (1)

[Claims] 1. A semiconductor light emitting device characterized in that a region of the semiconductor light emitting device that takes in light has a step shape, and each corner of the step shape has a rounded shape.