A redundant thin-film transistor (TFT), which has multiple sub-TFTs sharing one gate, is presented and studied. This transistor can be fabricated with two photomasks. It has transfer characteristics similar to those of a conventional single-channel TFT, except for (1) the negative-direction shift of the curve in the low drain current range, (2) the two-stage turn-on mechanism in the high drain current range, and (3) the high photoleakage current at the high drain voltage. The first phenomenon is due to the inclusion of electron accumulation interfaces in the semiconductor layer. The second phenomenon is caused by the sequential turn-on of various sub-TFTs at various gate voltages. The last phenomenon can be explained by the photoresistor characteristics of the top a-Si:H layer. 1995 American Institute of Physics.
