Initial degradation of base-emitter junction in carbon-doped InP/InGaAs HBTs under bias and temperature stress

Bias-temperature stress tests were performed to examine the stability of base-emitter junction characteristics of carbon-doped InP/InGaAs heterojunction biopolar transistors (HBT's). Two different kinds of degradation modes were observed from the Gummel I-V characteristics. One is characterized by the gradual increase in a nonideal base current. The generation of the nonideal current strongly depends on the crystallographic orientation of the emitter mesa. The other degradation mode was observed when a large current (200 kA/cm/sup 2/) was injected under a high ambient temperature (180/spl deg/C). This degradation is characterized by an initial decrease in turn-on voltage and significant drop in current gain.