Stability of hydrogenated amorphous silicon thin film transistors on polyimide substrates

摘要

The inverted staggered hydrogenated amorphous silicon thin film transistors (a-Si:H TFT) were fabricated on 6 μm thick polyimide substrate at temperatures below 300℃. The a-Si:H TFT off current is below 10~(-12) A, the on/off current ratio is ～10~7, the threshold voltage is ～2 3 V, field effect mobility is ～ 0.5 cm~2/Vs, and the subthreshold slope is ～0.4 V/decade. The stabilities of a-Si:H TFTs were studied and the device parameters determined before and after a bias stress of V_(GS) = 20 V for t= 10, 10~2, 10~3 and 10~4s. The threshold voltages shifted to higher values and on/off ratio decreased with the duration of bias stress. The device characteristics were measured in the dark and under the light illumination. Threshold voltages and on/off current ratio both decreased, Temperature dependant measurements of transfer and output characteristic of a-Si:H TFT in the range from 22℃ to 125℃ were also investigated. When temperature is increased threshold voltages decreased and the field effect mobility increased.