Temperature dependent leakage currents in polycrystalline silicon thin film transistors

We have studied the origins of the leakage current in polycrystalline silicon (poly-Si) thin film transistors. Temperature dependent transfer characteristics were measured as a function of drain voltage. Three kinds of leakage current were introduced to explain the experimental results. The leakage current may arise from the generation current at very low drain voltage, and may result in the same activation energy between leakage current and conductivity of undoped poly-Si. The leakage current may be due to the thermionic field emission via grain boundary defects in the intermediate drain voltage region. At high drain voltage and high negative gate voltage, the leakage current may result from the field enhanced tunneling of electrons in the valence band to the conduction band via grain boundary traps.