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 10 12 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 (L G =1.2µm) had current and power gain cut-off frequencies, f T and f max , of 2.9GHz and 10GHz, respectively.