Characterization of high Mg content MgZnO ultraviolet photodetectors with noise properties

This study examined MgZnO thin films grown on quartz substrates using radio frequency magnetron sputtering. These films with varying Mg content were used to fabricate metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PDs). The best sample with optimized properties was obtained using a Mg content of 20%. The relatively high Mg content could effectively suppress the dark current to a value of the order of 10^-13 A. The PD exhibited an on-off ratio of seven orders of magnitude; its photo-responsivity increased with the increasing Mg content, which caused the suppression of the dark current. The UV-to-visible rejection ratio could be up to five orders of magnitude. Furthermore, the noise equivalent power (NEP) and the normalized detectivity (D∗) of the PD fabricated with 20%Mg were determined as 6.6×10^-15 Wand 6.5×10^-14 cmHz^0.5W^-1, respectively. These results indicate that an increase in the Mg content could reduce the dark current and the noise by effectively suppressing the donor-like defects.