Leakage current mechanisms in top-gate nanocrystalline silicon thin film transistors

The leakage current in the top-gate nanocrystalline silicon (nc-Si:H) thin film transistors was examined at various temperatures in an attempt to deduce the underlying off-state conduction mechanisms. Under high gate bias, the leakage current can be attributed to the thermal emission of trapped carriers at the midgap grain boundary states at low drain bias, while the behavior is reminiscent of the Poole–Frenkel emission in the drain depletion region at high drain bias. In contrast, Ohmic conduction through the bulk nc-Si:H channel layer seems to be the dominant mechanism of the leakage current under low gate bias.