Patent ID: 6683332
Filing Date: 2004-01-27
Classification: H01L

Abstract:
A heterojunction bipolar transistor comprising:a low-concentration n-type collector layer formed on a semi-insulating substrate; a high-concentration p-type base layer formed on the collector layer; a low-concentration n-type emitter layer formed on the base layer; a base ohmic electrode which is made of a single layer or a plurality of layers and which is formed on a base protective layer that is a portion of the emitter layer; a high-concentration n-type emitter contact layer formed so as to cover regions of the emitter layer except the base protective layer; an emitter ohmic electrode which is made of a single layer or a plurality of layers and which is formed on the emitter contact layer; a base-use alloyed reaction layer formed under the base ohmic electrode, and an emitter-use alloyed reaction layer formed under the emitter ohmic electrode; and wherein the base-use alloyed reaction layer extends through the base protective layer so as to reach the base layer and the emitter-use alloyed reaction layer is formed only within the emitter contact layer so that the emitter-use alloyed reaction layer does not reach the emitter layer.