Amorphous-InGaZnO Thin-Film Transistors Operating Beyond 1 GHz Achieved by Optimizing the Channel and Gate Dimensions

Amorphous indium-gallium-zinc oxide (a-InGaZnO or a-IGZO) has already started replacing amorphous silicon in backplane driver transistors for large-area displays. However, hardly any progress has been made to commercialize a-IGZO for electronic circuit applications mainly because a-IGZO transistors are not yet capable of operating at gigahertz frequencies. Here, nanoscale a-IGZO thin-film transistors (TFTs) are fabricated on a high-resistivity silicon substrate with a Ta 2 O 5 gate dielectric. Carrier mobilities up to 18.2 cm 2 V −1 s −1 have been achieved. By optimization of the TFT channel length and contact overlap, we are able to demonstrate current gain and power gain cutoff frequencies at 1.24 and 1.14 GHz, respectively, both beyond the 1-GHz benchmark. Such a performance may have implications in developing at least medium performance, a-IGZO-TFTs-based circuits for low-cost or flexible electronics.