A model of electrical conduction across the grain boundaries in polycrystalline-silicon thin film transistors and metal oxide semiconductor field effect transistors

Abstract

An electrical conduction model of carrier transport across the grain boundaries (GBs) in polycrystalline silicon (PX-Si) films is developed by considering four conduction mechanisms, a Gaussian energy distribution for GB interface states and the GB scattering effects. The model is applicable over a wide range of temperature and grain size. It is found that the GB scattering potential and the GB distribution parameter are function of temperature but are independent of doping density and grain size. The conduction model is able to explain the dependence of transfer and output characteristics of thin film transistors (TFTs) on the temperature and grain size in the strong inversion regime. The variation of effective mobility and drain current for n-channel TFTs and metal oxide semiconductor field effect transistors with gate bias voltage and grain sizes is also studied. A satisfactory agreement is obtained between the theoretical investigations and the available experimental data.