INVESTIGATION OF LOW TEMPERATURE FREQUENCY CHARACTERISTICS OF POLYSILICON EMITTER BIPOLAR TRANSISTORS
多晶硅发射极晶体管的低温频率特性研究

The low temperature frequency characteristics of polysilicon emitter bipolar transistors are investigated, considered the carrier freezingout effect and trapping effect of shallow energy impurities in semiconductors. It shows that the base sheet resistance Rdb increases quasi-exponentially at low temperature due to carrier freezingout, which results in the degradation of frequency characteristics of the transistors at low temperature. The base and emitter transit time increase and the cutoff frequency decreases at low temperature due to the trapping effect of shallow energy level impurities. Those should be considered carefully in the design of devices for low temperature operation.