radiation response of npn bipolar transistors at various emitter junction biases

At various dose rates, ionizing radiation response of NPN bipolar transistors at three kinds of base-emitter junction biases was investigated. The results show that the radiation damages are most significant at base-emitter junction reverse bias and minimal at forward bias when irradiated at high or low dose rate. Furthermore, the radiation damage is more severe at low dose rate for the same bias, i.e. enhanced low dose rate sensitivity (ELDRS). The influence of base-emitter junction bias on ELDRS effect is obvious. The ELDRS effect is most significant for base-emitter junction forward bias, while it is least for reverse bias. The mechanisms of these results were discussed.