Avalanche-induced effects in polysilicon thin-film transistors

A comparison of experimental data and two-dimensional numerical simulations of polysilicon thin-film transistors (TFTs) is presented. It is shown that avalanche multiplication causes both the kink effect in the output characteristics and the reduction of threshold voltage in short-channel device. It is shown that exactly the same physical model for avalanche multiplication gives very good agreement between simulations and experimental data for both these effects. It is demonstrated that it is the presence of grain boundaries or traps in the polysilicon that causes avalanche effects to be much greater than in comparable single-crystal silicon devices.<<ETX>>