High signal/noise ratio deep UV detector with maximum response at 230 nm based on mix-phase MgZnO deposited under high laser energy condition

Abstract

A Mix-phase MgZnO thin film was fabricated on the c-plane sapphire substrate (Mg0.4Zn0.6O target) under high laser energy density condition by the PLD method. The internal quantum efficiency of the detector based on the mix-phase MgZnO thin film at 230 nm deep UV light reached 86% at 40 V bias voltage. And the Iuv(230 nm)/Idark ratio of the MgZnO detector reached 864 at 40 V bias voltage, which is mainly caused by both the higher internal gain of the detector at deep UV light and its smaller Idark. The high internal gain of the detector is mainly due to the higher density of interfaces between the different structure of MgZnO grains in the mix-phase MgZnO thin film, which is caused by the higher laser energy density deposition condition certified by contrast experiments. The small Idark of the detector is mainly caused by the higher barriers in the mix-phase MgZnO thin film and more cubic MgZnO in the mix-phase MgZnO thin film, and higher laser energy density deposition condition and O-rich c-plane sapphire substrate surface are key factors, which also agree with the contrast experiments results. So when the mix-phase MgZnO thin film that is constituted by both a small number of narrower band gap hexagonal MgZnO and a large number of wide band gap cubic MgZnO is used in the deep UV detector, and the difference in band gaps between different structures of MgZnO is relatively higher, a higher signal/noise ratio of the device at 230 nm deep UV light is gained, which is meaningful for developing high-performance deep UV detection technology.