Determination of interface-state density and mobility ratio in silicon surface inversion layers

Abstract

A method has been proposed to deduce the energy distribution of interface states and the mobility ratio of carriers simultaneously from Hall effect measurements at two different temperatures. Using this method, the interface-state density N ss and the mobility ratio r of carriers were determined on both n-channel and p-channel silicon MOS transistors. The result indicates that N ss determined in this method is very small near the center of the energy gap and increases as the energy of the states approaches the band edges. The interface-state density inside the conduction and the valence band was found as high as 1013cm-2eV-1. The value of mobility ratio was found to depend both on temperature and surface-carrier density. Increase of mobility ratio with decreasing carrier density was observed in all samples, it is interpreted as due to diffuse scattering and to Coulomb scattering by localized interface charges.