Mobility Enhancement and OFF Current Suppression in Atomic-Layer-Deposited ZnO Thin-Film Transistors by Post Annealing in O2

The impacts of postdeposition annealing in O
₂
on the electrical performance of atomic-layer-deposited ZnO thin-film transistors (TFTs) have been investigated. The TFTs are fabricated on transparent quartz substrates with Al
₂
O
₃
dielectrics, ZnO active layers, and Cr/Au electrodes. The best field-effect mobility of 21.3 cm
²
/Vs and a large ON/OFF current ratio of 10
⁷
are obtained under 400°C annealing treatment in O
₂
. Furthermore, analysis indicates that reduction of OH bonds in both ZnO and Al
₂
O
₃
layers is the key issue to achieve the excellent properties.