Influence of Source and Drain Electrodes on Device Performance of ZnO Thin Film Transistors

Abstract

In this study, thin film transistors (TFT) with ZnO as the channel layer and HfO2 as the gate dielectric were fabricated by radio frequency magnetron sputtering. The electrical properties of the TFT devices related to the Al and Au electrodes were investigated. From the drain current (IDS) vs the drain-source voltage (VDS) curve of the TFT, IDS can reach 0.3 mA for Al electrodes at the gate voltage (VGS) = 14 V and VDS = 10 V, while it is 0.13 mA for Au. From the transfer properties curve, the former yields a threshold voltage of 3 V, and a sub-threshold swing of 1.78 V/decade; while the latter has 4 V and 1.88 V/decade, respectively. The result indicates that the electrical properties of TFT device with Al electrodes are better than Au. The smaller work function with the Al electrodes is the key to TFT devices (Al: 4.28 eV < Au: 5.1 eV).