Surface-scattering effects in polycrystalline silicon thin-film transistors

Abstract

Mobility reduction, induced at high gate fields by scattering with surface acoustic phonons and surface roughness, has been investigated in self-aligned polycrystalline silicon (polysilicon) thin-film transistors (TFTs). The analysis of this effect can be influenced by the presence of parasitic resistance effects, and a precise evaluation of this effect has been obtained by measuring the transfer characteristics in devices with different channel lengths. In this way, we could reliably determine the mobility reduction effect, which was then analyzed by using two-dimensional numerical simulations. The mobility reduction in polysilicon TFTs can be accurately described by Lombardi’s model, originally proposed for c-Si metal-oxide-semiconductor field-effect transistors.