MgO (100) as an affordable support for heteroepitaxial growth of high-quality -Ga₂O₃ thin films and related highly-sensitive solar-blind UV photodetectors

Heteroepitaxial growth of high-quality beta-Ga2O3 thin films on foreign substrates is of crucial importance for achieving high-performance power-electronic and optoelectronic devices with affordable prices. Herein, we demonstrate realization of heteroepitaxial growth of high-quality beta-Ga2O3 films on MgO(100) via pulsed laser deposition, and achievement of related highly-sensitive solar-blind ultraviolet photodetectors (SBUVPDs). Under optimized oxygen pressure (7 Pa), single-phase, (100)-oriented, and atomically-smooth beta-Ga2O3 films were grown epitaxially on MgO(100), consisting of unique 8-12 nm-wide columnar nanodomains. Atomically-esolvable aberration-corrected transmission electron microscopy unveiled initial growth of a cubic.-phase transition layer of similar to 8 nm thickness, and directly visualized occurrence and preferable location of oxygen vacancies at domain walls in the further grown beta-Ga2O3 film. Density-functional-theory simulations rationalized the formation of columnar nanodomains in terms of energetics, and presumably identified the nanodomains interface orientations as (11 (2) over bar)/(1 (12) over bar). The heteroepitaxial beta-Ga2O3(100)/MgO(100) film-based photodetector demonstrates excellent performance, featured with exceedingly-low dark current, remarkably-high light-to-dark current ratio, and ultrahigh responsivity and detectivity (I-dark = 0.6 pA, I-light/I-dark = 1.47 x 107, R = 191 A/W, D*=3.08 x 1015 Jones) as well as fast response speed towards 255 nm-UV detection. This work highlights MgO (100) as a suited yet affordable foreign substrate for heteroepitaxial growth of high-quality beta-Ga2O3 films towards further development of high-performance devices such as SBUVPDs.