Ultrasensitive UV-C detection based on MOCVD-grown highly crystalline ultrawide bandgap orthorhombic K-Ga2O3

Abstract

Orthorhombic kappa-Ga2O3, as one of the Ga2O3 polymorphs, is considered a promising as ultrawide bandgap material for extreme environment devices. It is considered more superior than the conventional group III-V compound semiconductors and silicon carbides in extreme environments demanding material/device characteristics of high-voltage, high-temperature, high-pressure, high-impact, and high-radiation. In this study, we demonstrate ultrasensitive ultraviolet-C (UV-C) detection using Si-doped orthorhombic kappa-Ga2O3 photodetectors. A 150 nm thick kappa-Ga2O3 film was grown on a 2-inch diameter sapphire (a-Al2O3) wafer via metal organic chemical vapor deposition (MOCVD) method. The crystallinity of orthorhombic kappa-Ga2O3 film was investigated by X-ray diffraction (XRD) and transmission electron micro-scopy (TEM). The ultrawide bandgap of approximately 4.9 eV was confirmed by UV transmittance measurement. For UV-C detection analysis, a planar device with a channel length of 20 mu m was fabricated using Au/Ti metal contacts on the orthorhombic kappa-Ga2O3 film. The device doped under 15 sccm SiH4 flow rate showed ultrahigh photoresponse of similar to 72.1 A/W, I-on/I-off of-14, and decent rise ( similar to 0.35 s) and decay (similar to 1.79 s). Our results will contribute to the understanding on a new material phase of kappa-Ga2O3, as well as on developing optoelectronics devices with high radiation hardness suitable for operation in extreme environments.