An Au/Ni/Au/Ge/Pd ohmic contact system on n-type InGaAs was studied and applied to AlGaAs/GaAs heterojunction bipolar transistors (HBTs). Good ohmic behavior was achieved by rapid thermal annealing (RTA) at temperatures up to 400 °C, and the specific contact resistance was reduced to low-10-6 Ω cm2. However, by annealing at temperatures above 400 °C the characteristics were deteriorated by intermixing and phase reaction of the ohmic metals and InGaAs substrate. The HBTs using the Au/Ni/Au/Ge/Pd ohmic contact scheme showed reliable dc and rf performances with strong dependence on the ohmic contact, especially emitter ohmic contact with RTA temperature. © 1997 American Institute of Physics.