Degradation of InGaAs/InP double heterojunction bipolar transistors under electron irradiation

The dc characteristics of InGaAs/InP double heterojunction bipolar transistors (DHBT's) are studied under high-energy (similar to 1 MeV) electron irradiation up to a fluence of 14.8 x 10(15) electrons/cm(2). The devices show an increase in common emitter current gain (h(fe)) at low levels of dose (<10(15) electrons/cm(2)) and a gradual decrease in h(fe) and an increase in output conductance for higher doses. The decrease in h(fe) is as much as similar to 80% at low base currents (similar to 10 mu A) after a cumulative dose of 14.8 x 1015 electrons/cm(2) The observed degradation effects in collector current-voltage (I-V) characteristics are studied quantitatively using a simple SPICE-like device model. The ovarall decrease in h(fe) is attributed to increased recombination in the emitter-base junction region caused by radiation-induced defects. The defects introduced in the collector-base junction region are believed to be responsible for the observed increase in the output conductance.