The extraction of electrical parameters for MOSFETs with applications to low temperature

The authors examine six models for predicting triode region MOSFET behavior. The six models are formed from the combination of two channel charge models and three carrier velocity models. The channel charge and velocity descriptions are well documented in the literature, but only four of the models have been compared with experiment. It is shown that all six models predict identical MOSFET characteristics for sufficiently small drain voltages. It is shown that, at temperatures high enough that channel carrier freezeout is negligible, it is acceptable to extract MOSFET parameters from the transfer characteristics using methods derived from the simple square law model without velocity saturation. However, due to channel carrier freezeout onto the minority impurity sites for device bodies which contain both donors and acceptors, these methods are invalid at low temperatures. It is also shown that the hole saturation velocity in the channel increases with decreasing temperature. Between room and liquid-nitrogen temperatures, the increase is about 44%