Dependence of thin film transistor characteristics on low-angle grain boundaries of (100)-oriented polycrystalline silicon thin films

Abstract

Parallel and perpendicular n-channel and p-channel TFTs were developed on highly (100)-oriented polycrystalline silicon thin films that had low-angle grain boundaries. The n-channel TFTs exhibited excellent characteristics. A low leakage current of 10−11 A μm−1, an ON/OFF current ratio of 106, and a sub-threshold slope of 114 mV dec−1 were observed in the perpendicular TFT. These values were better than those of parallel TFT, however, its electron field effect mobility of 480 cm2 V−1 s−1 was twice smaller than that of parallel TFT. The cross low-angle grain boundaries strongly impacted on TFTs’ performance and Their barrier potential was calculated from the measured leakage current of parallel and perpendicular TFTs based on Levinson equation. Contrastingly, characteristics of parallel and perpendicular p-channel TFTs were similar due to uninfluenced by grain boundaries. An averaged hole field effect mobility of 148 cm2 V−1 s−1 was observed with dominantly (100)-oriented silicon crystals.