High Performance Aluminum-Doped ZnO Thin Film Transistors with High-K Gate Dielectrics Fabricated at Low Temperature

We report on the fabrication and characteristics of low-driven-voltage and high mobility thin film transistors (TFTs) using Aluminum-doped ZnO as an active channel layer grown by using radio frequency (rf) magnetron sputtering technique. The AZO-TFTs are fabricated on glass substrates at room temperature. The TFT device structure used in this study is a bottom gate type, which consists of high-K HfO2 film as the gate dielectric and indium tin oxide (ITO) as source and drain electrodes. The sputtering and post-annealing conditions of the gate insulators are optimized for leakage current and TFT performances. The device shows a low threshold voltage of 2.2 V, an high on/off ratio of 1.0 x 10(7), a high field effect mobility of 26.1 cm(2)N . s, a subthreshold swing of 0.25 V/decade, and the off current of less than 10(-12) A at a maximum device processing temperature of 180 degrees C. The AZO-TFTs is a very promising low-cost optoelectronic device for the next generation of invisible electronics due to transparency, high mobility, and low-temperature processing.