Tradeoff regimes of lifetime in amorphous silicon thin-film transistors and a universal lifetime comparison framework

We report that the dependence of the lifetime of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) versus channel sheet resistance (R(sheet)) exhibits two distinctly different regimes. At low R(sheet) (high gate electric field) the lifetime is strongly dependent on R(sheet), decreasing as R(sheet) is decreased. At high R(sheet) (low gate electric field), the lifetime becomes independent of R(sheet). These two regimes of lifetime are dominated by different degradation mechanisms. By including hydrogen dilution in the deposition process, the extrapolated time for the 10% and 50% decay of the TFT current under dc operation in the low gate field regime can be raised to over 2 and 1000 yr, respectively. (C) 2009 American Institute of Physics. [doi:10.1063/1.3238559]