Transparent thin film transistors using ZnO as an active channel layer and their electrical properties

Bottom-gate-type thin film transistors using ZnO as an active channel layer (ZnO-TFT) have been constructed. The ZnO layers were deposited using pulsed laser deposition at 450degreesC at an oxygen pressure of 3 m Torr, and the material that was formed had a background carrier concentration of less than 5 X 10(16) cm(-3). A double layer gate insulator consisting of SiO2 and SiNx was effective in suppressing leakage current and enabling the ZnO-TFT to operate successfully. The I-on/I-off ratio of ZnO-TFTs fabricated on Si wafers was more than 10(5) and the optical transmittance of ZnO-TFTs fabricated on glass was more than 80%. These results show that it is possible to fabricate a transparent TFT that can even be operated in the presence of visible light. 2003 American Institute of Physics. [DOI: 10.1063/1.1534627].