A light-shield a-Si TFT with low dark-leakage currents

Abstract

A light-shield amorphous silicon (a-Si:H) thin film transistor (TFT) with low dark leakage current is developed. The a-Si:H island edge of this TFT is selectively oxidized without affecting the metal/n/sup +/ a-Si:H layer contact quality, and thus the hole current flowing through the parasitic metal/intrinsic a-Si:H contact at that edge can be blocked. Using this technique, the TFT with effective mobility of 0.7 cm/sup 2//Vsec, subthreshold swing of 0.55 V/dec, and threshold voltage of 1.5 V can be achieved. In addition, the leakage current of the TFT is as low as 0.5 pA at high negative gate bias of -10 V and drain voltage of 10 V.