Voltage-tunable uvc–uvb dual-band metal–semiconductor–metal photodetector based on ga₂o₃/mgzno heterostructure by rf sputtering

Dual-band metal–semiconductor–metal (MSM) photodetectors (PDs) with a Ga₂O₃/MgZnO heterostructure were fabricated by radio frequency (RF) sputtering, which can detect ultraviolet C (UVC) and ultraviolet B (UVB) bands individually by controlling different bias voltages. A PD with the annealing temperature of Ga₂O₃ at 600^◦C can improve the crystal quality of Ga₂O₃ thin film and exhibit the least persistent photoconductivity (PPC) effect. However, a PD with the annealing temperature of Ga₂O₃ at 600^◦C cannot achieve a voltage-tunable dual-band characteristic. On the contrary, the PD without annealing can suppress the carriers from the bottom layer of MgZnO thin film at a lower bias voltage of 1 V. At this time, the peak responsivity at 250 nm was mainly dominated by the top layer of Ga₂O₃ thin film. Then, as the bias voltage increased to 5 V, the peak detection wavelength shifted from 250 (UVC) to 320 nm (UVB). In addition, the PD with a 25 nm–thick SiO₂ layer inserted between Ga₂O₃ and MgZnO thin film can achieve a broader operating bias voltage range for dual-band applications.