Patent ID: 6451659
Filing Date: 2002-09-17
Classification: H01L

Abstract:
A method of making a heterojunction bipolar transistor, comprising:epitaxially growing at least three semiconductor layers of III-V semiconductor material as an upper layer, a middle layer, and a lower layer on a substrate; providing the middle layer with a first conductivity type and the upper and lower layers with a second conductivity type so that the middle layer can function as a base of the heterojunction bipolar transistor while the upper layer can function as either an emitter or a collector of the heterojunction bipolar transistor; providing a first mask having a width l over the at least three semiconductor layers; implanting electrically insulating ions in the upper layer on at least two opposite sides of the first mask to form electrically insulating regions in the upper layer on opposite sides of a central region of said second conductivity type; forming a second mask of width L over the three semiconductor layers, said width L being greater than the width l; and etching at least a part of the electrically insulating regions on the opposite sides of said central region using the second mask so as to define an upper layer mesa above the middle base layer, said upper layer mesa including the central region formed to occupy the middle of the upper layer mesa between the electrically insulating elements on each opposite side thereof.