In this paper we report on the processing for silicon phototransistor which is equipped with polysilicon/silicon emitter structure. In order to evaluate the effect of polysilicon/silicon interface on phototransistor’s performance, we compared the devices’ Gummel plot and emitter contact resistance(Re) by different pretreatment (routine RCA clean or RCA clean + HF dip) before Low Pressure Chemical Vapor Deposition (LPCVD) of polysilicon, and following different temperature thermal annealing after polysilicon preparation. It’s observed that additional HF dip can make phototransistor’s current gain curve milder, emitter resistance lower and good controllability of characteristic parameter, but with little penalty in term of gain peak value.
