Influence of lateral electric field on the anomalous leakage current in polysilicon TFT'S

An unique approach is proposed to investigate the anomalous leakage current in polysilicon thin-film transistors (TFT's). The approach utilizes test structures which have nonuniform film thickness at the drain, source and channel regions, These structures are used to analyze the influence of the lateral electric field on the leakage current. An order of magnitude reduction in leakage current at high drain bias is observed in the thick drain TFT structure compared to the thin drain structure. The improvement on the leakage current is due to the reduction in lateral electric field at the thicker drain. The influence of the lateral electric field on the anomalous leakage current is investigated with the grain boundary trapping effects separated out.