High mobility thin film transistors with transparent ZnO channels

We have fabricated high performance ZnO thin film transistors (TFTs) using CaHfOx, 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 300degreesC. The process temperature can be reduced to 150degreesC without much degrading the performance, showing the possibility of the use of polymer substrate.