ZnO film with ultra-low background electron concentration grown by plasma-assisted MBE using Mg film as the buffer layer

High quality ZnO epilayer with background electron concentration as low as 2.6 × 1014 cm−3 was obtained by plasma-assisted MBE on c-sapphire using a thin Mg film as the buffer layer. High-resolution XRD measurement shows a sharp (0 0 2) peak with full width at half maximum (FWHM) of only 0.029°. Photoluminescence spectroscopy presents a weak defect-related near-edge emission. A metal–semiconductor–metal (MSM) typed photodetector based on the material demonstrates a response of ∼43 A/W under the bias of 1 V and an ON/OFF ratio of 104. This un-doped ZnO with ultra-low background electron concentration could be a promising starting material for p-type doping.