Enhanced Performance of Self-Powered γ-Ray Irradiated MSM Deep UV Photodetector Based on MOCVD-Grown ZnGa2O4 for Space Exploration

The utilization of device for the space explorations, the active material of the device must show resilience toward cosmos radiation. In this work, the radiation hardness of ZnGa2O4-based deep ultra-violet (DUV) photodetectors (PDs) is examined using gamma-ray irradiation. Responsivity of the photodetector at zero bias is found to improve from 0.98 to 1.94 mA W-1, the dark current increased from 0.11 to 5.6 pA, while photo-to-dark current ratio (PDCR) increased the from 3.2 x 10(3) to 3.1 x 10(4) and the photocurrent decay time improved from 220 to 190 ms. The high-resolution X-ray photoelectron spectra (HR-XPS) of O 1s core level peak is deconvoluted into two main peaks namely, O(I) and O(II), where the lattice oxygen of ZnGa2O4 is identified by the O(I) peak, while its surface oxygen defect is represented by O(II). A clear increment is observed in the percentage of oxygen defect peak, O(II), from 6.82 to 53.19% after 200 kGy. Also, the device remains undeteriorated after 200 kGy irradiation, indicating it to be a radiation-hard device. These characteristics allow ZnGa2O4 DUV PDs to function effectively in cosmic radiation environments with the capability to operate on zero-bias, regardless of the gamma-radiation.