Fabrication of InGaP/Al/sub 0.98/Ga/sub 0.02/As/GaAs oxide-confined collector-up heterojunction bipolar transistors

A partially oxidized Al/sub 0.98/Ga/sub 0.02/As layer was introduced between the emitter and base of collector-up heterojunction bipolar transistors (C-up HBTs) to suppress the leakage current and improve the current gain. Dependence of device current gain and leakage current on oxidation temperature was investigated. At lower oxidation temperature, the current gain can be effectively improved. Current gain and base sheet resistance were 79 and 203 ohm/sq. for the C-up HBT oxidized at 400/spl deg/C.