Effects of oxygen pressure on PLD-grown Be and Cd co-substituted ZnO alloy films for ultraviolet photodetectors

We report on the synthesis of Be and Cd co-substituted ZnO (BexCdyZn1-x-yO) quaternary alloy films on c-plane sapphire substrates by pulsed laser deposition. The results show that all deposited films exhibit single-phase wurtzite structure with a surface roughness less than 1.5 nm. By adjusting the O-2 pressure during growth, the optical bandgap of the film is tuned from similar to 3.3 to similar to 3.52 eV. At 5 V bias, the BexCdyZn1-x-yO-based photodetector exhibits a remarkable photoresponse in the ultraviolet region with low dark current (similar to 16.2 pA) and high detectivity (9.31 x 10(10) Jones). The rise and decay times of the photodetectors based on BexCdyZn1-x-yO (order of seconds) are clearly faster than those based on pure ZnO (order of minutes). Higher O-2 pressure results in better crystalline quality of BexCdyZn1-x-yO film and thus lower dark current and faster photoresponse in the device due to the decrease of oxygen vacancy-related defects under oxygen-rich growth conditions. These results indicate that oxygen pressure plays an important role in the growth of high-quality BexCdyZn1-x-yO alloy films, which have great potential in fabricating high-performance ultraviolet photodetectors. (c) 2020 Elsevier B.V. All rights reserved.