Performance enhancement of ZnGa2O4 Schottky type deep-ultraviolet photodetectors by oxygen supercritical fluid treatment

Abstract

For semiconductor device applications such as FinFET, MEMS, 2D materials, and wide bandgap materials, reliability is one of the most powerful key factors for commercialization in the industry. ZnGa2O4 deep ultraviolet (DUV) photodetectors (PDs) have been studied for their reliability and hence have been examined using the accelerated life test (ALT), which has shown the poor reliability of the device and device degradation such as high leakage current and poor rise time falling time (Tr/Tf) ratios. Therefore, in this paper, we proposed a method to enhance device performance by a non-destructive post-treatment method with low temperature and high-pressure oxygen supercritical fluid (SCF-O) for DUV photodetectors. This method not only improved the device performance but allowed it to perform even better than the as-grown sample. X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscope analyses corroborated better crystallinity with a smaller number of interstitial defects followed by mathematical modelling using density functional theory. The on/off ratio increased from 102 to 105 and had an improved rise time and fall time ratio (Tr/Tf). The responsivity for the SCF-O treated ZnGa2O4 PDs (@240 nm) increased to 639 A/W as compared with that (486 A/W) of as-grown sample. The first-principles DFT-GGA calculations were used to explain the relationship between the formation energies of defects in the oxygen treatment on the ZnGa2O4 epitaxial layers and agreed well with the experiment results. As per our knowledge, our study was the first to present this post-treatment method for DUV photodetectors, which could increase the lifetime of semiconductor devices.

Keywords

• Supercritical fluids with oxygen
• Accelerated life test
• Zinc gallate
• Schottky type deep ultraviolet photodetector
• Density functional theory