Critical Study of the Saturation Drain Voltage and the Multiplication Current in MOSFETs at Liquid Helium Temperature

Abstract

In this paper, several empirical methods for the extraction of the saturation drain voltage V DSAT of cryogenic MOSFETs, operating at liquid helium temperature (LHT) will be compared. Their advantages and drawbacks are discussed in detail. It is concluded that the most accurate results are obtained from the output resistance based method. The consequences of the V DSAT extraction on the multiplication current (I M ) and drain-current kink modeling, will be outlined. From an extensive study of I M for different processing splits, it is concluded that the critical field for velocity saturation at 4.2 K increases with gate overdrive voltage, due to the transverse field dependence of the effective mobility.