MgO (1 0 0) as an affordable support for heteroepitaxial growth of high-quality β-Ga2O3 thin films and related highly-sensitive solar-blind UV photodetectors

Abstract

Heteroepitaxial growth of high-quality β-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 β-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 β-Ga2O3 films were grown epitaxially on MgO(100), consisting of unique 8–12 nm-wide columnar nanodomains. Atomically-resolvable aberration-corrected transmission electron microscopy unveiled initial growth of a cubic γ-phase transition layer of ∼ 8 nm thickness, and directly visualized occurrence and preferable location of oxygen vacancies at domain walls in the further grown β-Ga2O3 film. Density-functional-theory simulations rationalized the formation of columnar nanodomains in terms of energetics, and presumably identified the nanodomains interface orientations as (112¯)/(11¯2¯). The heteroepitaxial β-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 (Idark = 0.6 pA, Ilight/Idark = 1.47 × 107, R = 191 A/W, D*=3.08 × 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 β-Ga2O3 films towards further development of high-performance devices such as SBUVPDs.