Ultraviolet Photodetector Based on Mg $_{\rm x}$ Zn $_{1 - {\rm x}}$ O Thin Films Deposited by Radi

The Mg_x Zn_{1 - x}O (0 les x les 0.36) films were deposited on an Al₂O ₃ substrate by radio frequency magnetron sputtering. The X-ray diffraction analysis showed the deposited MgZnO films have a single-phase hexagonal wurtzite structure. The optical bandgap of Mg_xZn_{1- x}O films exhibited a linear increase from 3.25 to 4.04 eV with the Mg content x increasing from 0 to 0.36. Correspondingly, the cutoff wavelength of the resultant detectors varies from 380 to 310 nm, indicating that the detecting wavelengths of the Mg_xZn_{1 - x}O metal-semiconductor-metal ultraviolet photodetectors (MSM-UPDs) can be controlled by simply adjusting the Mg contents in the film. The resultant MgZnO MSM-UPDs with various Mg contents exhibit promising performances. At a bias voltage of 20 V, the dark currents of all MSM-UPDs are smaller than 0.6 nA. The rejection ratio of the MSM-UPDs varies from 701 to 769, slightly dependent on the Mg contents.