ON THE UNIVERSAL ELECTRIC-FIELD DEPENDENCE OF THE ELECTRON AND HOLE EFFECTIVE MOBILITY IN MOS INVERSION-LAYERS

A simple and direct method for the extraction of the parameter eta entering the electric field expression for the MOSFET inversion layer mobility is proposed. The method, which relies on the gate and substrate voltage dependence of the effective mobility, allows us to clearly demonstrate that the effective mobility in an inversion layer is not in general a universal function of the electric field as is usually admitted for room temperature. This suggests, in agreement with physical arguments drawn from mobility data obtained at low temperature, that the electron and hole mobility must be, from a more general point of view, a function of the inversion charge Q(i) and of the depletion charge Q(d), but not of a linear combination of these variables such as etaQ(i) + Q(d).