Self-aligned InAlAs/InGaAs heterojunction bipolar transistor with a buried subcollector grown by selective epitaxy

We report the first microwave characterization of an In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistor (HBT) with a buried InGaAs subcollector grown by selective epitaxy. The study compares two HBT's having identical 2×10 μm2self-aligned emitter fingers but different subcollectors. Improvement in microwave performance of the selectively-grown HBT over the conventional HBT was observed due to the reduced parasitic base-collector capacitance achieved by incorporating the selectively-grown buried subcollector.