Characteristics of the ZnO thin film transistor by atomic layer deposition at various temperatures

ZnO thin films were deposited by atomic layer deposition (ALD) at various temperatures and the resulting electrical and chemical properties were examined. The fraction of O–H bonds in ZnO films decreased from 0.39 to 0.24 with increasing processing temperatures. The O/Zn ratio decreased from 0.90 at 70 °C to 0.78 at 130 °C. The carrier concentration and resistivity changed sharply with decreasing temperature. The ZnO thin film transistors (TFTs) were fabricated at processing temperatures of 70 to 130 °C and the electrical properties of the TFT were as follows: the field-effect mobility ranged from 8.82 × 10−3 to 6.11 × 10−3 cm2 V−1 s−1, the on/off current ratio ranged from 1.28 × 106 to 2.43 × 106, the threshold voltage ranged from −12.5 to 14.7 V and the subthreshold swing ranged from 1.21 to 24.1 V/decade. The electrical characteristics of the ZnO TFT were enhanced as the processing temperature decreased.