Far-UVC Field Emission Device at 226 nm and its Sub-Nanometer thick GaN/AlN Quantum Well Anode

Abstract

We report on unique features of ultra-thin GaN/AlN quantum wells and demonstrate a new field emission device for human-safe disinfection with an external quantum efficiency of 18% and superior reliability, as compared to far-UVC LEDs. We investigate the behavior of a Shockley-Read-Hall recombination via Al vacancies-oxygen complexes in AlN barriers as a function of GaN well thickness and come to the conclusion that direct relaxation of confined states via mid-gap traps is prohibited and the main mechanism limiting the quantum efficiency (QE) is the carrier escape followed by non-radiative SRH recombination in the AlN barriers. As a consequence, the QE is highly dependent on the defect density, QW width and temperature which allowed us to reach a descent emissions at 226 nm wavelength although at wall plug efficiency being low, at 0.02%. We build a complete Light-Current-Voltage model and find that present device performance is limited by the self-heating and by the Child's space charge effect, both limitations can be easily addressed with some additional engineering efforts.