Performance enhancement of MgZnO ultraviolet photodetectors using ultrathin Al2O3 inserted layer

In this study, the magnesium zinc oxide (MgZnO) films and ultrathin alumina (Al2O3) inserted layers were subsequently deposited on sapphire substrates using a plasma-enhanced atomic layer deposition system, and applied in metal-semiconductor-metal ultraviolet (UV) photodetectors (MSM-UPDs). The dark current of the MgZnO MSM-UPDs was decreased from 1 to 0.34 nA with an increase in Al2O3 layer thickness from 0 to 5 nm. The ultrathin Al2O3 inserted layer effectively passivated the dangling bonds on the MgZnO surface and blocked leakage current. At a bias voltage of 5V, the maximum UV-visible rejection ratio of the MgZnO MSM-UPDs was 1.78 x 10(3) with 5-nm-thick Al2O3 inserted layer. Furthermore, the noise equivalent power and detectivity of MgZnO MSM-UPDs with 5-nm-thick Al2O3 inserted layer were improved from 1.26 x 10(-14) W and 2.50 x 10(13) cm Hz(1/2) W-1 to 0.93 x 10(-14) W and 3.40 x 10(13) cm Hz(1/2) W-1 in comparison with MgZnO MSM-UPDs without Al2O3 inserted layer. The high performances of MgZnO MSM-UPDs were achieved by using ultrathin Al2O3 inserted layer. (C) 2016 American Vacuum Society.