THE EFFECTS OF IONIZING-RADIATION ON GAAS ALGAAS AND INGAAS ALINAS HETEROJUNCTION BIPOLAR-TRANSISTORS

GaAs/AlGaAs and InGaAs/AlInAs Heterojunction Bipolar Transistors (HBTs) have been exposed to Co-60 gamma-ray doses up to 100 MRad. The d.c. current gain of GaAs/AlGaAs devices showed small increases for doses up to 75 MRad, due to a faster decrease in base current relative to collector current. After 100 MRad, none of the original devices were operational because of failure of the base-collector contact metallization (TiPtAu). Devices with either Be- or C-doped base layers showed the same response to the gamma-ray doses. The InGaAs/AlInAs HBTs showed a small decrease (< 10%) in current gain after a total dose of 88 MRad and appear to be somewhat more resistant to damage from accumulated doses of radiation than comparable GaAs devices. GaAs/AlGaAs devices exposed to transient (120 nsec) pulses of high energy electrons show rapid recovery of both collector and base currents, with no long transient responses observed. Numerical simulations of the recovery of both GaAs- and InP-based HBTs after transient doses of ionizing radiation suggest that both are relatively immune to damage up to dose rates of 10(11) Rad s-1 with faster recovery of the GaAs devices because of the shorter recombination times in this material.