Pulsed laser deposition of ZnO grown on glass substrates for realizing high-performance thin-film transistors

摘要

We report characterization of ZnO thin-film transistors (TFTs) on glass substrates fabricated by pulsed laser deposition (PLD). ZnO films were characterized by X-ray diffraction (XRD), atomic force microscopy and Hall effect measurements. The XRD results showed high c-axis-oriented ZnO(0002) diffraction corresponding to the wurtzite phase. Moreover, the crystallization and the electrical properties of ZnO thin films grown at room temperature are controllable by PLD growth conditions such as oxygen gas pressure. The ZnO films are very smooth, with a root-mean-square roughness of 1 nm. From the Hall effect measurements, we have succeeded in fabricating ZnO films on glass substrates with an electron mobility of 21.7 cm~2/V s. By using the ZnO thin film grown by two-step PLD and a HfO_2 high-k gate insulator, a transconductance of 24.1 mS/mm, a drain current on/off ratio of 4.4 × 10~6 and a subthreshold gate swing of 0.26 V/decade were obtained for the ZnO TFT.