Temperature dependence improvement of polycrystalline-silicon tunnel field-effect thin-film transistor

Abstract

Trap-assisted tunneling (TAT) mechanism dominates the subthreshold leakage current and ambipolar transport behavior of tunnel field-effect transistor (TFET) with polycrystalline-silicon (poly-Si) channel. The unwanted ambipolar transport behavior of poly-Si TFET can be suppressed by the employment of gate-to-drain underlap structure to increase the tunneling distance near the drain side when the TFET is operated at the negative gate voltage. The gate-to-drain underlap length of TFET would also exhibit series resistance effect and strong temperature effect on the on-state current (ION). The strong temperature dependent series resistance effect and bandgap narrowing effect cause the poly-Si TFET to exhibit temperature instability of the on-state current. In order to improve the temperature instability of the on-state current, the ammonia plasma treatment has been performed to passivate the defects and reduce the trap state density of poly-Si film. The trap state density reduction of poly-Si can improve the field-effect mobility of transport carrier and reduce the series resistance effect, resulting in the reduction of the temperature dependence of ION. Consequently, the improved temperature dependent ION of poly-Si TFET can be obtained, and it is useful for the development of poly-Si thin-film transistor and its applications in the high resolution display industry and three-dimensional integrated-circuit.