An approach for fabricating a self-aligned InP/InGaAs heterojunction bipolar transistor (HBT) with InGaAs dummy emitter layer was demonstrated. The self-aligned emitter-base structure employs crystallographically defined emitter contact (CDC) technology to define a desired emitter-to-base contact spacing. An anisotropic wet etching of the InGaAs dummy emitter layer grown on the HBT layer structure leads to the crystallographically etched profiles to configure the shape of the emitter contact. InP/InGaAs HBTs demonstrated good current-voltage characteristics with a current gain more than 40 and a knee voltage of approximately 0.5 V up to a collector current density of 1 x 10(5) A/cm(2), indicating the effectiveness of the new self-alignment technology. (C) 2004 The Electrochemical Society.