Comprehensive study on the transport mechanism of amorphous indium-gallium-zinc oxide transistors

High-performance thin-film transistors (TFTs), in which the channel material consisted of amorphous indium-gallium-zinc oxide (a-IGZO) with a bottom gate architecture, were fabricated for array applications. It was found that the dependence of the field-effect mobility on the channel length was greatly affected by the value of the contact resistance (R-C). A high contact resistance (RCW similar to 200 Omega cm) resulted in a significant drop (similar to 22.3%) in the normalized field-effect mobility for the short channel device (10 mu m), while contact-limited behavior was hardly seen for the device with a low contact resistance (RCW similar to 23 Omega cm). The difference in the channel length dependence of the field-effect mobility was comprehensively investigated based on the conduction mechanism. The fabricated n-channel a-IGZO TFTs with W/L = 10/10 mu m exhibited a field-effect mobility of 12.6 cm(2)/V s, threshold voltage of 4.7 V, on/off ratio of 10(8), and subthreshold gate swing of 0.56 V/decade. (C) 2008 The Electrochemical Society.