Urbach energy dependence of the stability in amorphous silicon thin-film transistors

We investigate the relationship between the stability of amorphous silicon thin-film transistors (a-Si:H TFTs) and the bulk properties of a-Si:H films. Threshold voltage shifts in a-Si:H TFTs are characterized by the thermalization energy Eth for different times and temperatures and fitted by {1+exp[(Eth−Ea)/kT0]}−2. We find that kT0 exhibits a clear correlation to the Urbach energy, but the more significant parameter Ea seems to depend only on the deposition-induced microstructure and not on the Urbach energy, the hydrogen content, or the hydrogen diffusion coefficient.