InGaAs/InP HBTs with a buried subcollector fabricated by selective epitaxy

Summary form only given. The authors demonstrate the fabrication of a novel HBT (heterojunction bipolar transistor) with a buried subcollector layer using selective growth techniques. The effective base-collector overlap area is drastically reduced with respect to a conventional device. The process consists of two distinct steps: (1) definition of a buried subcollector layer using chloride-transport VPE (vapor-phase epitaxy), and the subcollector is created by planarizing growth over an InP:Fe substrate with etched openings; and (2) regrowth, using organometallic VPE, of the collector, base, and emitter layers. The requirements of excellent planarization and high-quality regrown layer material are both achieved. Chloride-transport VPE allows a very high degree of planarization with very little excess growth on top of the substrate. This feature makes the selective growth process self-limiting and relatively independent of mask layout, a common problem with many selective epitaxy approaches