Behavior of MOS inversion layers at low temperature

Metal-oxide-silicon capacitance voltage curves in the inversion range at liquid nitrogen temperature are interpreted. Buildup of the inversion charge is very slow, but once it is established it cannot be readily injected. A forward bias of about 0.25 volt must be reached across the space-charge region before noticeable injection occurs. The true inversion capacitance voltage curve can be measured by allowing a long time for equilibration at each bias point.