A model for the conduction in polycrystalline silicon thin film transistors

The aim of this paper is the analysis, prediction and optimisation of polysilicon thin film transistors (TFTs) in both « on » and « off » states. We have established a physical model which accounts for the grain, the grain surface and grain boundaries. The conduction mechanisms and the exchange between electron and hole populations are explicitly considered. Field effects are included through the influence of carrier velocity saturation, impact ionisation and interband tunnel effect. A fair agreement between experimental characteristics and simulated results is obtained, and the simulations allow a good insight into the main mechanisms controlling the TFT operation modes. Keywords: Polysilicon, dangling bonds, band tail states, TFT, simulation, generation-recombination, impact ionisation, interband tunnel effect