Method of manufacturing heterojunction transistors with self-aligned metal contacts
A method of manufacturing heterojunction transistors having self-aligned contacts. In manufacturing a heterojunction bipolar transistor, a collector and a base layer are deposited on a substrate. A masking layer is deposited on the base layer and selectively etched to form an aperture therein, exposing the base layer. An emitter having a mesa structure is grown epitaxially on the exposed base layer to produce lateral overhang portions. The overhang portions may be formed by continuing the epitaxial growth to form lateral overgrowth portions overlapping the masking material. The masking layer is removed and self-aligned contacts are formed to the base and emitter regions using the lateral overhang portions which provide separation between the emitter structure and the contacts to the base layer.