Effects of Backgate Voltage on Electrical Characteristics of Poly-Si Thin Film Transistors Fabricated on Stainless-Steel Substrate

Abstract

High mobility p-channel polycrystalline Si thin film transistors (poly-Si TFTs) are fabricated on flexible stainless-steel substrates coated with 500-nm-thick SiO2 and 50-nm-thick SiN films. The electrical characteristics of mobility, threshold voltage and subthreshold slope are first measured as a function of backgate voltage V BG of from -26 V to +20 V applied on stainless-steel substrate. Mobilities show small dependence on V BG. Threshold voltages, however, have dependence of decreasing with increasing V BG. Subthreshold slopes also show concave-shaped dependence on V BG. The results indicate that electrical characteristics of poly-Si TFTs are controlled by simply applying voltages to the substrate. Thus, application of backgate voltage are very important for design advanced poly-Si TFT integrated circuits and to secure stable operation of the circuits.