Wet Chemical Synthesis of Ultrathin γ-Ga 2 O 3 Quantum Wires Enabling Far-UVC Photodetection with Ultrahigh Selectivity and Sensitivity.

As compared to solar-blind ultraviolet (UV) photodetectors (PDs), far-UVC PDs not only show some irreplaceable advantages but also are more challenging to be developed. To solve this challenge, we report herein a soft template-assisted solvothermal route to synthesize ultrathin γ-Ga2 O3 quantum wires (UQWs) with diameters down to 1-2 nm. These UQWs all exhibit a cluster-like absorption feature with a strong peak located between 190 and 230 nm and an edge below 250 nm, allowing highly selective absorption to far-UVC light. Notably, their normalized absorption coefficients were experimentally and theoretically confirmed to increase obviously with decreasing their diameters. Self-powered photoelectrochemical-type PDs based on Ga2 O3 QWs of 1.7 nm diameter were therefore fabricated, exhibiting an excellent far-UVC detection performance with an unprecedented ultrahigh spectral selectivity ( R 210 nm / R 250 nm = 452). As a proof of concept, this paper offers a new idea for developing ultrawide bandgap semiconductor materials and devices by leveraging a strong quantum confinement effect.