Depletion-mode TFT made of low-temperature poly-Si

This brief reports the fabrication and characterization of a depletion-mode p-channel low-temperature polycrystalline silicon (poly-Si) thin-film transistor (TFT). The poly-Si channel was significantly doped by B ions to make a hole-accumulation layer at zero gate voltage. The depletion-mode poly-Si TFT is normally ON-state, so that the current can flow from the source to the drain at zero gate voltage. The TFT exhibited a field-effect mobility of 60 cm/sup 2//V/spl middot/s, a threshold voltage of 18 V, an on/of current ratio of 10/sup 6/, and a gate voltage swing of 1.1 V/dec.