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 transfe r characteristics were measured as a function of drain voltage. Three kinds of leakage current were introduced to explain the experimental r esults. The leakage current may arise from the generation current at v ery low drain voltage, and may result in the same activation energy be tween leakage current and conductivity of undoped poly-Si. The leakage current may be due to the thermionic field emission via grain boundar y defects in the intermediate drain voltage region. At high drain volt age and high negative gate voltage, the leakage current may result fro m the field enhanced tunneling of electrons in the valence band to the conduction band via grain boundary traps. (C) 1997 American Institute of Physics.