Impact of Ge profiles on neutron-induced displacement damage effect in SiGe HBT

The impact of Ge profiles on neutron-induced displacement damage effect in SiGe HBT is investigated by calibrated three-dimensional TCAD simulation. With the same integrated Ge content across base layer, the device with a flat (Box) Ge profile exhibits less base current degradation than that with a gradient (Triangular) or a compromised (Trapezoidal) Ge profile. Simulation results indicate that the susceptibility to displacement damage is closely related to the modulation of carrier recombination rate in EB depletion region by Ge profile. A high Ge content at the EB junction can suppresses the back-injection of holes from base into emitter, thereby suppressing the trap-assisted carrier recombination in EB depletion region. The study suggests that the Ge profile should be carefully tailored when designing SiGe HBTs for radiation environments.