The improved performance of a transparent ZnO thin-film transistor with AlN/Al₂O₃ double gate dielectrics

This paper reports on the fabrication of stable and improved performance of transparent ZnO thin-film transistors (TFTs) with AlN/Al₂O ₃ double gate dielectrics. AlN films reduce the surface roughness of the channel/dielectric interface due to an excellent lattice match with the ZnO film. Al₂O₃ films, which have a large band offset between the channel layers, are helpful to reduce the gate leakage current. Good device characteristics have been obtained from the AlN/Al₂O₃ TFT with a field effect mobility of 4.3 cm² V^-1 s ^-1, an on-off current ratio of 2 × 10⁵ and a sub-threshold slope of 0.45 V/decade. By diminishing the charge trap density in the interface, the threshold voltage change from the hysteresis of the transfer characteristics was minimized to 0.3 V. These results should increase the prospects of using transparent TFTs for flat panel display applications.