Ultraviolet photodetector based on Mg_xZn_1-xO films using plasma-enhanced atomic layer deposition

A plasma-enhanced atomic layer deposition (PE-ALD) system was used to deposit magnesium zinc oxide (Mg_xZn_1-xO) films with various Mg content (x). The Mg_xZn_1-xO films were applied to metal-semiconductor-metal ultraviolet (UV) photodetectors (MSM-UPDs) as an active layer. The Mg content in the Mg_xZn_1-xO films was modulated by adjusting the ZnO-MgO cycle ratios to 15:1, 12:1, and 9:1. Correspondingly, the Mg content in the Mg_xZn_1-xO films characterized using an energy dispersive spectrometer was 0.10, 0.13, and 0.16, respectively. The optical bandgap of the Mg_xZn_1-xO films increased from 3.56 to 3.66 eV with an increase in Mg content from 0.10 to 0.16. The peak position of photoresponsivity for the Mg_xZn_1-xO MSM-UPDs was also shifted from 350 to 340 nm. The UV-visible rejection ratios of the Mg_xZn_1-xO MSM-UPDs were higher than 3 orders of magnitude. In addition, excellent detectivity and noise equivalent power for the Mg_xZn_1-xO MSM-UPDs were observed at a bias voltage of 5 V. The high performance of the Mg_xZn_1-xO MSM-UPDs was achieved by PE-ALD at a low temperature.