Enhancement of ZnO thin film transistor performance by high-dose proton irradiation

The object of this study was to improve the performance of ZnO thin film transistors (TFTs) by exposing them to high-dose proton irradiation. A rapid thermal annealing (RTA) process was necessary to improve the interface characteristics between the source-drain electrodes and the channel layer for the high performance of ZnO-TFTs. However, this affected the resistivity of the ZnO channel layer; it was dramatically decreased during the RTA process. As a result, the RTA-treated ZnO-TFTs did not show the proper off-state characteristics. In order to control the electrical properties of the channel layer, we exposed the RTA-treated ZnO-TFTs to 6.1 MeV of proton irradiation beam energy at fluences from 6.7 x 1012 cm-2 to 6.5 x 1014 protons-cm-2. The resulting resistivity of the ZnO thin film increased after the high-dose proton irradiation. In addition, we studied the structural and electrical properties and the variations in the native defects of ZnO thin films. The field effective mobility of ZnO-TFTs increased from 1.65 to 4.12 cm2/V s after both the RTA and the high-dose proton irradiation. We obtained an enhancement of ZnO-TFT performance using high-dose proton irradiation.