ZnO NANOCRYSTALLINE HIGH PERFORMANCE THIN FILM TRANSISTORS

Abstract

In this study, nc - ZnO films deposited in a Pulsed Laser Deposition (PLD) system at various temperatures were used to fabricate high performance transistors. As determined by Transmission Electron Microscope (TEM) images, nc - ZnO films deposited at a temperature range of 25°C to 400°C were made of closely packed nanocolums showing strong orientation. The influences of film growth temperature and post growth annealing on device performance were investigated. Various gate dielectric materials, including SiO 2, Al 2 O 3, and HfO 2 were shown to be suitable for high performance device applications. Bottom-gate FETs fabricated on high resistivity (>2000 ohm-cm) Si substrates demonstrated record DC and high speed performance of any thin film transistors. Drain current on/off ratios better than 1012 and sub-threshold voltage swing values of less than 100mV/decade could be obtained. Devices with 2μm gate lengths produced exceptionally high current densities of >750mA/mm. Shorter gate length devices (LG=1.2μm) had current and power gain cut-off frequencies, f T and f max , of 2.9GHz and 10GHz, respectively.