MODELING OF ELECTRON-MOBILITY IN SILICON MOS INVERSION AND ACCUMULATION LAYERS AT LIQUID-HELIUM TEMPERATURE

A study of the effective mobility in silicon MOS inversion and accumulation layers at liquid helium temperature is reported. It is demonstrated, using MOS devices of various technologies, that the effective mobility,μe, at liquid helium temperature can be represented by a bell-shaped function of the inversion (or accumulation) charge Qn which has the generic form [formula-omitted] where nm is the maximum mobility and Qm a critical charge of the order of 1-3 x 1012q/cm2, which are parameterised functions of the bulk charge in the case of enhancementmode devices. This mobility law, which can be considered as a universal feature of the transport at the Si-SiO2 interface, enables an analytical modelling of enhancement and depletion mode MOS transistors to be obtained at liquid helium temperature. © 1990, The Institution of Electrical Engineers. All rights reserved.