Determination of interface and bulk traps in the subthreshold region of polycrystalline silicon thin-film transistors

A simple method to determine the interface and bulk density of states in polycrystalline silicon thin-film transistors is presented. The energy distribution of the interface trap density has been extracted from analysis of the transfer characteristics in the subthreshold region of operation. Using the obtained interface state distribution, the energy distribution of the bulk traps has been determined by fitting the surface potential at each gate voltage with analytical theoretical model. Both interface and bulk traps were found to consist of deep states with constant density near the mid-gap and band-tails with density increasing exponentially, with the energy when the trap energy approaches the conduction band-edge.