High Mobility Thin Film Transistors with Transparent ZnO Channels

We have fabricated high performance ZnO thin film transistors (TFTs) using CaHfO x buffer layer between ZnO channel and amorphous silicon–nitride gate insulator. The TFT structure, dimensions, and materials set are identical to those of the commercial amorphous silicon (a-Si) TFTs in active matrix liquid crystal display, except for the channel and buffer layers replacing a-Si. The field effect mobility can be as high as 7 cm 2 ·V -1 ·s -1 for devices with maximum process temperature of 300°C. The process temperature can be reduced to 150°C without much degrading the performance, showing the possibility of the use of polymer substrate.