Switch-on transient behavior in low-temperature polycrystalline silicon thin-film transistors

We report upon the measurement and simulation of the switch-on transient of polycrystalline silicon (poly-Si) thin-film transistors. The measurement of the switch-on transient reveals an unexpectedly long transient that cannot be explained by the theory adopted for single-crystal silicon-on-insulator (SOI) devices. Contrary to the SOI case, the transient is seen to increase with source-drain voltage. In order to explain the experimental findings, we have performed simulations of the transient and found that the results are heavily dependent upon the density of states in the band gap and their capture cross sections. Only when energy-dependent cross sections are adopted do the calculations correctly reproduce the steady-state and overshoot currents, and also the transient duration. A physical interpretation of this phenomenon is presented. (C) 2000 American Institute of Physics. [S0003- 6951(00)02349-4].