Low-temperature operation of polycrystalline silicon thin-film transistors

The influences of the grain boundary traps on poly-Si TFT (thin-film transistor) device characteristics were evaluated in detail by examining the low-temperature device characteristics. It was found that the absolute value of threshold voltage significantly increases and the field-effect mobility considerably decreases at low temperature because the influences of the grain boundary traps become more pronounced. As a result, the drain current is strikingly reduced specifically in n-channel TFTs when the temperature is decreased. Meanwhile, the kink effect is suppressed at low temperature due to the increased influences of the grain boundary traps. The hydrogenation treatment mitigated the drain current reduction at low temperature and enhanced the kink effect.