Compressively Strained p-Type Mg-Doped Two-Dimensional Ga₂O₃ with a Direct Band Gap and Anisotropic Hole Mobility

The unintentional n-type conductivity and inherent poor mobility of novel two-dimensional (2D) Ga2O3 severely restrict their applications. One of the effective pathways to achieve p-type conductivity theoretically is substituting the trivalent Ga3+ as a group IIIA oxide with the divalent Mg2+ ion in group IIA. Here, the detailed band structures and hole transport properties of Mg-doped 2D Ga2O3 with an energetically favorable occupation on the GaI site (MgGaI) are investigated by employing first-principles calculations involving the Perdew–Burke–Ernzerhof (PBE) and Heyd–Scuseria–Ernzerh (HSE) functionals, deformation potential (DP), and Boltzmann transport theories, as well as ab initio molecular dynamic (AIMD) simulations. The appearance of an impurity band above the valence band demonstrates the p-type doping feature of MgGaI, accompanying the indirect to direct bandgap transformation upon Mg substitution. Applying the biaxial strain modulations from −8% compressive to +8% tensile, the direct bandgap feature can be efficiently retained under compressive strains. Furthermore, the hole mobilities of −8% compressively strained MgGaI along the x and y directions are estimated as 0.11 and 630.9 cm2 V–1 s–1, respectively, compared to those of 0.01 and 326.00 cm2 V–1 s–1 for the unstained case. The retention of the p-type direct bandgap features and the boosted hole mobility anisotropy of compressively strained Mg-doped β-Ga2O3 film shed light on its promising applications as high-power electronic devices.