Slow transients in polyimide-passivated InP-InGaAs HBTs: effects of UV irradiation, thermal annealing and electrical stress

The effects of UV irradiation, thermal annealing and electrical bias on the base current instability in polyimide (PI)-passivated InP-based heterojunction bipolar transistors (HBTs) have been studied. The base current transient could be effectively suppressed by UV irradiation. The suppression of current transient by UV irradiation can be attributed to the reduction of the near interface trap density in the PI, which has long-term stability at room temperature. However, baking the device at a temperature higher than 100 /spl deg/C may induce a significant increase in PI trap density as well as the broadening of spatial electron trap distribution causing the enhancement of current transient, and the current transient induced by electrical stress could be directly related to the device self-heating through thermal annealing effect.