Prevention of base dopant out-diffusion using a heterostructure-emitter in GaInP/GaAs heterojunction bipolar transistors

Abstract

Zinc-doped GaInP/GaAs heterojunction bipolar transistors (HBTs) grown by MOCVD were fabricated. Characteristics of HBTs with an undoped spacer layer and an n-type GaAs set-back layer (heterostructure-emitter) between base and emitter were investigated. The results show that the base dopant out-diffusion was effectively prevented in heterostructure-emitter bipolar transistors (HEBTs). In addition, a current gain of 100 at the collector current density of 1*10 -2 A cm -2 and an offset voltage of 57 mV were obtained for Zn-doped HEBTs. In comparison with carbon-doped HBTs, HEBTs Offer a higher current gain at a low current level, a smaller offset voltage and better uniformity in characteristics across the wafer.