LOW-TEMPERATURE MIGRATION-ENHANCED EPITAXY OF BASE MATERIAL FOR ALGAAS GAAS HETEROJUNCTION BIPOLAR-TRANSISTORS/

Migration enhanced epitaxy (MEE) was used in this work to grow p+-GaAs at the substrate temperature of 300-degrees-C for the base of AlGaAs/ GaAs heterojunction bipolar transistors. The results indicated that th e low-temperature MEE-grown p+-GaAs epitaxial layers (p = 1 X 10(19) - 1 X 10(20) CM-3) exhibited a crystalline quality comparable to those g rown by standard MBE at a substrate temperature of 570-degrees-C. AlGa As/GaAs HBTs with low-temperature MEE-grown bases doped at p almost-eq ual-to 2 X 10(19) cm-3 were fabricated by using a self-alignment techn ique. For the devices with the conventional MBE-grown base, secondary ion mass spectroscopy depth profiles showed a significant Be diffusion into the AlGaAs emitter and as a consequence, the devices showed no c urrent gain. For the devices with the low-temperature MBE-grown base, there was a negligible Be penetration into the emitter and the devices exhibited a common-emitter dc current gain of 13.