Impact of Ring-Shaped Collector Contact on Total Ionizing Dose Susceptibility of Vertical n-p-n Bipolar Transistors

The impact of ring-shaped collector contact (RCC) on total ionizing dose (TID) susceptibility of 40-V vertical n-p-n bipolar transistors is investigated. The( 60)Co gamma-ray irradiation experiment shows that the devices with RCC suffer less current gain degradation than their counterparts with conventional collector contact structure, which is independent of the emitter area and bias condition during irradiation. Technology computer-aided design (TCAD) simulation results indicate that the enhancement in radiation tolerance of the RCC devices should be attributed to the mitigation of trap-assisted carrier recombination at the Si/SiO2 interfaces near emitter-base (EB) junction rather than the concentration or distribution variations of radiation-induced traps. Moreover, the mitigation of carrier recombination in RCC devices could result from the creation of new current flow paths that suppress the diffusion of injected electrons toward the trap-enriched Si/SiO2 interfaces.