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

The dc characteristics of InGaAs/InP double heterojunction bipolar transistors (DHBTs) are studied under high-energy (/spl sim/1 MeV) electron irradiation up to a fluence of 14.8/spl times/10/sup 15/ electrons/cm/sup 2/. The devices show an increase in common-emitter current gain (h/sub fe/) at low levels of dose (<10/sup 15/ electrons/cm/sup 2/) and a gradual decrease in h/sub fe/ and an increase in output conductance for higher doses. The decrease in h/sub fe/ is as much as /spl sim/80% at low base currents (/spl sim/10 /spl mu/A) after a cumulative dose of 14.8/spl times/10/sup 15/ electrons/cm/sup 2/. The observed degradation effects in collector current-voltage (I-V) characteristics are studied quantitatively using a simple SPICE-like device model. The overall decrease in h/sub 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.