High performance solar-blind UV detector with Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O double layer structure on MgO substrate

Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O double layer structure UV detectors are made on single structure MgO substrate by PLD method, and the effect of different thickness top MgZnO layer on the UV response characteristics of the detector are studied. Compared with the single layer MgZnO detector that made by Mg_0.3Zn_0.7O target, the Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O double layer detector with 30 nm top layer, shows much higher deep UV response (21.3 A W^-1at 265 nm), much smaller dark current(66.9 pA) and much higher signal-to-noise ratio (2.8 × 10⁵) at 25 V bias voltage. And the device also shows relative high response (23.1 A W^-1) at 235 nm deep UV light at 25 V bias voltage, which is mainly attributed by the bottom MgZnO layer with higher Mg composition. When the top layer is 66.7 nm thick, the response of the Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O detector reached 228.8 A W^-1at 255 nm under 25 V bias voltage, the signal-to-noise ratio of which is 10573 under 20 V bias voltage, and the near UV response of the device is also big because of more h-MgZnO in top MgZnO layer. When the top layer reached 90.2 nm, there are much more h-MgZnO in the top MgZnO layer, the peak response of the Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O detector is just 6.65 A W^-1at 320 nm under 25 V bias voltage, the signal-to-noise ratio of which is 1248. The high Mg composition bottom MgZnO decrease the dark current of the Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O detector, both the 2DEG effect of the double layer structure and the amplify effect of the mix-phase MgZnO top layer, increased theI_uvand deep UV response of the Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O detector. Therefore, the double layer Mg_0.472Zn_0.528O/Mg_0.447Zn_0.553O detector is more sensitive at faint deep UV light compared with previous reported MgZnO detectors, and the Mg_xZn_1-xO/Mg_yZn_1-yO detector shows similarI_uvand signal-noise-ratio at faint deep UV light as high-temperature fabricated Al_xGa_1-xN/Al_yGa_1-yN detectors.