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 $(Rsheet)$ exhibits two distinctly different regimes. At low $Rsheet$ (high gate electric field) the lifetime is strongly dependent on $Rsheet$⁠, decreasing as $Rsheet$ is decreased. At high $Rsheet$ (low gate electric field), the lifetime becomes independent of $Rsheet$⁠. 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.