Microwave ZnO Thin-Film Transistors

We have developed ZnO thin-film transistor design and fabrication techniques to demonstrate microwave frequency operation with 2-mum gate length devices produced on GaAs substrates. Using SiO₂ gate insulator and pulsed laser deposited ZnO active layers, a drain-current ON/OFF ratio of 10¹², a drain-current density of 400 mA/mm, a field-effect mobility of 110 cm²/V ldr s, and a subthreshold gate voltage swing of 109 m/dec were achieved. Devices with Ti-gate metal had current and power gain cutoff frequencies of 500 and 400 MHz, respectively.