Structural, optical, and photoluminescence study of ZnO/IGZO thin film for thin film transistor application

• IGZO thin film deposited at low temperature is amorphous.
• IGZO thin film crystallizes at low temperature due to self-texturing of ZnO.
• ZnO/IGZO thin film is c- axis oriented, possesses less density of defects than a-IGZO.
• ZnO/IGZO thin film annealed at 450 °C exhibits lowest density of defects.
• ZnO/IGZO thin film annealed at 450 °C exhibits better TFTs performance than the device based on post-annealed IGZO film.

Highly transparent and c-axis oriented zinc oxide (ZnO)/indium gallium zinc oxide (IGZO) thin films have been fabricated by R.F. sputtering. The effect of annealing on physical properties of the films was investigated and compared with a-IGZO thin films. The films are wurtzite-type hexagonal structure similar to ZnO with [0 0 0 2] preferred direction and exhibit less density of defects. The TFTs fabricated with ZnO/IGZO films after annealing at 450 °C reveal smaller sub-threshold swing (SS~0.52 V/dec) and threshold voltage (Vth~1.3 V) than the TFTs (SS~0.82 V/dec, Vth~13.3 V) of a-IGZO thin film annealed at the same temperature.