Ultraviolet photodetectors based on MgZnO thin films

In this work, Ti/Au Ohmic contacts to both Mg(0.24)Zn(0.76)O and ZnO film-based metal-semiconductor-metal (MSM) photodetectors (PDs) were fabricated on glass substrates for comparative analysis. The transmittance spectra measured around the optical energy gap revealed that Mg(0.24)Zn(0.76)O films have a larger optical energy gap (3.54 eV) than ZnO films (3.25 eV). Mg(0.24)Zn(0.76)O MSM-structured ultraviolet (UV) PDs show a much higher UV-to-visible rejection ratio of 2.78 x 10(3) than those made of ZnO films. This can be attributed to the low dark current (0.08 pA) of the Mg(0.24)Zn(0.76)O UV PDs and the small full width at half maximum (0.34 degrees) of the Mg(0.24)Zn(0.76)O (002) x-ray diffraction peak, indicating better crystal quality than that of ZnO. With an applied bias of 5 V and illuminations at 350 and 380 nm, the Mg(0.24)Zn(0.76)O and ZnO film-based MSM PDs exhibited responsivities of 0.4 and 0.32 A/W, respectively. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3575552]