Аннотация:The effects of neutron irradiation on both Si bipolar junction transistor (BJT) and SiGe heterojunction transistor (HBT) are investigated using Synopsys/ISE TCAD tool. For this purpose the carrier lifetime degradation under irradiation models are included in the program. It was established that at fluence 4·10 13 cm -2 the Si BJT exhibited a degradation in current gain of 50% for high level and 80% for low level of E-B junction injection. For SiGe HBT at fluences as high as 10 15 cm -2 the degradation of peak current gain is less than 40%,and the devicemaintains a peak current gain of 80 - 100 after 10 15 cm -2 . The cut-off and maximum oscillations frequencies are small sensitive to neutron irradiation. The simulation results are in good agreement with experimental data.