光敏晶体管的中子位移损伤效应研究

通过开展光敏晶体管的反应堆中子辐照实验，获得位移效应实验结果，并分析位移损伤机理。研究发现，在3×10¹¹~5×10¹²cm^-2中子注量范围内，光敏晶体管增益和光响应度的下降导致集电极输出电流下降。增益的倒数与注量的增加呈线性关系，注入电流越大，线性关系的斜率越小。理论分析表明，通过提高基区掺杂水平或减小基区宽度，可提高增益的抗辐射水平；不同反向偏置电压下的初级光电流辐照前基本相同，随着辐照注量的增大，差异逐渐增大，反向偏置电压越大，初级光电流的退化越小；通过采用PIN结构或加大反向偏置电压来展宽耗尽区以减少受位移效应严重影响的扩散电流份额，可提高初级光电流的抗辐射水平。与PIN光电二极管不同，本实验注量范围内，光敏晶体管的暗电流随注量的增大而减小。

Study on Neutron Displacement Damage Effect in Phototransistor

Reactor neutron irradiation on phototransistor was investigated. Collector current of phototransistor decreased after exposure to neutron fluence from 3×10¹¹ to 5×10¹²cm^-2, which was attributed to the degradation of gain and photoresponsivity. The reciprocal of gain was linear with fluence and the slope of the line decreased with injected current increasing. Theoretical analysis shows that heavily doping base region or shortening base width can enhance radiation hardness of gain. The primary photocurrents under different reverse-biased voltages are basically equal before irradiation and gradually differ when neutron fluence increases, and the degradation is small for the high reverse-biased voltage. Radiation tolerance of primary photocurrent can be improved by applying PIN structure or increasing reverse-biased voltage which broaden depletion-region and lower the proportion of diffusion current which is very sensitive to radiation. The dark current of phototransistor decreases with fluence increaseing, which is different from that for PIN photodiode.