Effect of post-annealing temperatures on thin-film transistors with ZnO/Al2O3 superlattice channels

• Thin-film transistors (TFTs) of ZnO/Al2O3 superlattice channel were studied.
• Effect of annealing temperature of the TFTs was investigated.
• Electrical properties of superlattice TFTs were tuned by post-annealing.
• Increased conductivity was attributed to the interdiffusion within channels.
• Annealing temperature affected microstructure and electrical properties.

Oxide-based thin-film transistors (TFTs) were fabricated using ZnO/Al2O3 superlattice channels deposited by atomic layer deposition. Here, a post-annealing treatment was performed at various temperatures (200–550 °C) and the properties of the oxide TFTs were evaluated. An annealing temperature up to 250 °C showed enhanced TFT performance, while further increases in the annealing temperature resulted in an abruptly invisible switching property due to the high conductivity of the channel layers. With respect to annealing temperature, increased electrical conductivity in the superlattice films was attributed to the increase of conducting crystalline layers due to the inter-diffusion behavior between the ZnO and Al2O3 layers. The formation of the conducting layer was related to substitution by Al3 + ions into Zn2 + sites in the inter-diffusion region. The ZnO/Al2O3 superlattice TFT with the best field effect mobility, 30.2 cm2/Vs, was observed for an annealing temperature of 250 °C.