Method of fabricating light-emitting semiconductor device

Abstract

A light-emitting diode having a silicon substrate on which there are successively formed a buffer layer, a p-type nitride semiconductor layer, an active layer, an n-type nitride semiconductor layer, and a current spreading layer. The current spreading layer is a lamination of a first and a second sublayer arranged alternately a required number of times. Composed of different compound semiconductors, the alternating sublayers of the current spreading layer create heterojunctions for offering the two-dimensional gas effect. The current spreading layer is so low in resistivity in a direction parallel to its major surface from which light is emitted, that the current is favorably spread therein for improved efficiency of light emission. A front electrode in the form of a metal pad is mounted centrally on the major surface of the current spreading layer in ohmic contact therewith.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a Divisional of U.S. application Ser. No. 10 / 994,922 filed Nov. 22, 2004 (Atty. Docket No. TAK-0404), which claims priority to Japanese Patent Application No.2003-396151, filed Nov. 26, 2003.FIELD OF THE INVENTION [0002] This invention relates to a light-emitting diode or like semiconductor device made from chemical compounds, particularly those of Groups III-V elements, and to a method of making such a light-emitting device. BACKGROUND OF THE INVENTION [0003] A typical conventional compound semiconductor light-emitting device is a lamination of a baseplate of sapphire or silicon carbide or silicon, a buffer layer, an n-type semiconductor layer, an active layer, a p-type semiconductor layer, and a contact layer. Another example, taught by the U.S. Pat. No. 5,008,718 to Fletcher et al., is a lamination of a substrate, an n-type semiconductor layer, an active layer, a p-type semiconductor layer, and a current spreading...

AI Technical Summary

Benefits of technology

The present invention aims to improve the efficiency of a light-emitting device by introducing a current spreading layer with two sublayers of different compositions. This layer helps to generate carriers in the active layer and limits carrier overflow, resulting in higher efficiency and better response of the device. The current spreading layer can be thinner than conventional layers, which will less hinder the passage of light and incur less power loss. The invention also provides two methods for making the device, one of which involves a growth substrate for the current spreading layer and the other of which involves a support substrate for the active layer.

Problems solved by technology

The current flowing in this part of the active layer was wasted, not contributing to the net efficiency of the light emitting device.

Itself impervious to light, however, the annulus reduced by as much as 30 to 40 percent the surface area from which light was emitted, causing a corresponding drop in the efficiency of light production.

Additionally, the current spreading layer was not nearly so pervious to light as could be desired, absorbing so much light as to invite a significant diminution in the efficiency of light production.

The relatively thick current spreading layer proposed by the U.S. patent cited above is also objectionable from the standpoint of maximal light emission.

This layer has proved to absorb so much light as to cause a significant decrease in the efficiency of light emission.

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