Strain mediated ultra-high electron mobility in Ge-doped two-dimensional Ga2O3

Two-dimensional (2D) Ga2O3 has been of particular interest recently since it exhibits overwhelming superiority over bulk β-Ga2O3; however, efforts to modify the carriers of 2D Ga2O3 are few both theoretically and experimentally. In this work, we study the biaxial strain mediated electronic structures and transport properties of Ge-doped 2D Ga2O3 using first-principles calculations with Perdew–Burke–Ernzerhof functional and Boltzmann transport theory. The Ge-doped Ga2O3 shows excellent structure stability as suggested by its low formation energy of −3.99 eV, as well as phonon dispersion analysis and ab initio molecular dynamic simulation. The bandgap values of Ge-doped 2D Ga2O3 are tunable from 2.37 to 1.30 eV using biaxial strain from −8% compressive to +8% tensile because of the changeable σ* anti-bonding and π bonding states in the conduction band minimum and valence band maximum, respectively, as well as the decreased quantum confinement effect. Importantly, an ultra-high electron mobility up to 6893.43 cm2 V−1 s−1 is predicated in Ge-doped 2D Ga2O3 as the biaxial tensile strain approaches 8%. Our work highlights the enormous potential of Ge-doped 2D Ga2O3 in nanoscale electronics and suggests that Ge is an excellent dopant candidate toward optoelectronic applications.