Influence of an a-SiNx:H gate insulator on an amorphous silicon thin-film transistor

The effect of an a-SiNx:H gate insulator on the threshold voltage and field-effect mobility in amorphous silicon thin-film transistors has been investigated by using different compositions of a-SiNx:H, and the threshold-voltage shift is found to be reduced at an a-SiNx:H composition of x=1.0. Photoluminescence measurements reveal that the threshold-voltage shift for x<1.0 is due to electron trapping in the localized states of the a-SiNx:H layer, while that for x>1.0 is due to electron trapping in the deep states near the a-Si:H/a-SiNx:H interface, arising from lattice strain. Field-effect mobility decreases as x increases and is due to the increased number of deep states in the a-Si:H near the a-Si:H/a-SiNx:H interface.