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 thermali zation energy E-th for different times and temperatures and fitted by {1 exp[(E-th - E-a)/kT(0)]}(-2). We find that kT(0) exhibits a clear correlati on to the Urbach energy, but the more significant parameter E-a seems to de pend only on the deposition-induced microstructure and not on the Urbach en ergy, the hydrogen content, or the hydrogen diffusion coefficient. (C) 1999 American Institute of Physics. [S0003-6951(99)04922-0].