Mist-CVD Growth of Gallium Oxide for Developing Solar-Blind UV Photodetectors for
International Safeguards Applications

Gallium oxide (Ga2O3) is a compelling candidate material for radiation detection, particularly for the ultraviolet (UV) portion of the electromagnetic spectrum. Its exceptionally wide bandgap (up to 4.9 eV) renders it insensitive to thermal excitation. Moreover, as a compound semiconductor, the bandgap of gallium oxide can be tuned to further tailor its response spectrum to a given application, such as allowing for the isolation of signals in the deep UV. Furthermore, because of its radiation hardness, gallium oxide’s solar-blind functionality can be employed even in harsh environments. While solar-blind UV photodetectors have been studied extensively for uses in corona discharge detection, communications, and more, their uses in international safeguards have been underemphasized. Solid-state detection of Cerenkov light is at the heart of the International Atomic Energy Agency (IAEA) inspector’s modern toolkit. The Digital Cerenkov Viewing Device (DCVD) scans for bulk and partial defects in spent light-water reactor (LWR) fuel rods stored in cooling pools. Unfortunately, external filtration incurs large signal losses and still permits infrared leakage. Additionally, the DCVD lacks a tunable bandgap and has a poor radiation hardness that precludes it from submersion into a strong radiation field. To confront these shortcomings, we are developing a Cerenkov detector made from α-Ga2O3 and grown by mist chemical vapor deposition (mist-CVD). Mist-CVD has the advantage of low cost and relative simplicity and is well-suited to the lower temperature growth of the α-phase polymorph. This is done with the aim of eliminating noise like indoor fluorescent lighting while harnessing Ga2O3’s solar-blind imaging capabilities.