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 u p to 75 MRad, due to a faster decrease in base current relative to col lector current. After 100 MRad, none of the original devices were oper ational because of failure of the base-collector contact metallization (TiPtAu). Devices with either Be- or C-doped base layers showed the s ame response to the gamma-ray doses. The InGaAs/AlInAs HBTs showed a s mall decrease (< 10%) in current gain after a total dose of 88 MRad an d appear to be somewhat more resistant to damage from accumulated dose s of radiation than comparable GaAs devices. GaAs/AlGaAs devices expos ed to transient (120 nsec) pulses of high energy electrons show rapid recovery of both collector and base currents, with no long transient r esponses observed. Numerical simulations of the recovery of both GaAs- and InP-based HBTs after transient doses of ionizing radiation sugges t 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 short er recombination times in this material.