Accurate evaluation of effective mobility in Si MOSFETs at cryogenic temperatures using the quasi-static <i>C–V</i> method

Abstract We experimentally characterize surface carrier concentration and effective mobility of Si n-channel MOSFETs by using the split C–V method at temperatures from 300 K to 4 K. It is found that the capacitance in conventional split C–V decreases with increasing measurement frequency and that the influence is more pronounced at lower temperatures, leading to inaccuracy of estimated effective mobility. Therefore, we introduce a method to extract surface carrier concentration and resulting mobility accurately by using quasi-static split C–V (QSCV) measurements and experimentally show that effective mobility estimated by QSCV at 4 K is in good agreement with Hall mobility. As a result, we can conclude that QSCV is an effective method to extract the effective mobility of MOSFETs at cryogenic temperatures.