Multilayer MgZnO/ZnO thin films for UV photodetectors

MgyZn1-yO/ZnO thin films have been deposited on soda lime glass substrates by using sol-gel spin coating technique with varying Mg contents (y = 2, 4, 6, 8 at. %). X-ray diffraction (XRD) studies indicate that films exhibit the wurtzite phase with a preferential c-axis (002) orientation. The scanning electron micrographs revealed that at low doping level round and oval shaped microstructure were formed and on increasing Mg content nanoflower and nanoplate morphology were found. The transmittance of the thin films was measured in the wavelength range 300 nm-800 nm and the bandgap increased from 3.25 eV to 3.29 eV with increasing Mg content. The I-V measurements were performed in dark and illumination conditions show Ohmic behaviour. MgyZn1-yO/ZnO (y = 2 at. %) thin films show high stability and fast switching UV photoresponse behaviour. The highest responsivity of 0.16 A/W was obtained at 3.2 mW/cm2exposure of UV light (365 nm) at 5 V bias voltage.