[en] In this paper, MgZnO films were annealed at various temperatures (700–900 °C) and their effects on the electrical characteristics of Schottky-barrier photodetectors (SB-PDs) were studied. We show that the content of Mg atom increases with annealing temperature. On 900 °C annealing, the Mg content is determined to be as high as 49.2 at. %. However, no cubic-phase MgZnO segregation occurs in such high-temperature annealed MgZnO films, revealing the MgZnO film grown by radio-frequency sputtering is rather stable. Moreover, high-temperature (900 °C) annealing results in denser MgZnO film and smaller gap between the grains, leading to higher mobility and lower sheet resistance compared with low-temperature annealed MgZnO films. The enhanced performance results in the 900 °C annealed SB-PD exhibiting higher rectification ratio of 326 compared to the 800 °C annealed SB-PD that has a rectification ratio only 40. Further, lower sheet resistance reduces the turn-on voltage from  >200 V (for SB-PD with as-deposited MgZnO film) to 0.4 V (for SB-PD with 900°C annealed MgZnO film). Even at low (−10 V) bias-voltage, the 900 °C annealed SB-PD presents the highest ultraviolet (UV) responsivity (0.088 A/W) and UV-visible rejection ratio (2264) compared with the SB-PDs with low-temperature annealed MgZnO films at very high (−100 V) bias-voltage. (paper)