Enhanced Performance and Thermal Stability of a-Si:H TFTs

Abstract

We report the effect of anneal time on the performance and elevated temperature stability of hydrogenated amorphous silicon (a-Si:H) thin-film-transistors (TFTs). The sub-threshold swing and off-current are reduced by a factor of 2.5 and by almost two orders of magnitude for 48 h annealed TFTs, respectively when compared to unannealed TFTs. Furthermore, long annealed TFTs show significant elevated temperature stability when compared to the unannealed TFTs. The sub-threshold swing, hysteresis, electron mobility, and off-current are stable even at elevated temperatures. For all the TFTs at positive gate bias threshold voltage shift (Vt) follow a power law-dependence with time indicating state-creation mechanism. Life-time values for the 48 h annealed TFT shows improvement by a factor of 3 when compared to unannealed TFTs (when Vt is extrapolated to 10 V). The stability at elevated temperatures and better performance of long annealed TFTs is attributed to improved a-Si:H channel and/or the a-Si:H/insulator interface.