Leakage current of offset gate p- and n-channel excimer laser annealed polycrystalline silicon thin-film transistors

The leakage current I-L of offset gate n- and p-channel excimer laser annea led polycrystalline silicon thin-film transistors (polysilicon TFTs) has be en investigated experimentally. It has been found that the leakage current is almost independent of the polysilicon layer quality, in n-type polysilic on TFTs, I-L arises from band-to-band tunneling due to extension of the dra in junction to the gate end by diffusion of phosphorus ions fr om the drain contact within the offset region. In p-channel TFTs, I-L first increases r apidly and then saturates at high drain voltages. This leakage current beha vior is explained qualitatively by a model based on the change of the effec tive offset length, caused by the applied drain voltage on the positive ion s of boron, diffused from the drain contact within the offset region. (C) 2 001 Elsevier Science Ltd, All rights reserved.