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 (I_DS) vs the drain-source voltage (V_DS) curve of the TFT, I_DS can reach 0.3 mA for Al electrodes at the gate voltage (V_GS) = 14 V and V_DS = 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).

Keywords:

• ZnO-TFT
• bottom gate
• on/off current ratio
• HfO₂

Acknowledgements

This work is supported in partial by the National Nature Science Foundation of China (No. 51072049), STD and ED of Hubei Province (Grant Nos. 2009CDA035, 2008BAB010, 2010BFA016, and Z20091001).