P-type Ca-doped two-dimensional Ga₂O₃ with strain-modulated high hole mobility and anisotropy

Abstract The realization of p-type conductivity with substantial hole mobility remains challenging in emerged wide-bandgap two-dimensional (2D) β -Ga 2 O 3 . The substitution of Ca 2+ on Ga 3+ site is one of the efficient ways to achieve p-type conductivity theoretically. In this work, by employing first-principles calculations with Perdew–Burke–Ernzerhof and Heyd–Scuseria–Ernzerh hybrid functionals, deformation potential and Boltzmann transport theories, the structural stabilities, band structures, hole mobilities and p-type conductivities of Ca-doped 2D β -Ga 2 O 3 are systematic investigated. Firstly, the Ca dopant exhibits an energetically favorable substitution at the GaI site (Ca GaI ) under O-rich environment, accompanying with superior structural stabilities. Secondly, the electronic structure calculations demonstrate that the Ca impurity can induce a shallow acceptor level and act as an effective p-type dopant. Finally, ±8% strains have been used as a tuning knob in Ca GaI , which modulate the bandgaps from 4.73 to 3.76 eV. The hole mobility along y -direction is increased from 246.62 cm 2 V −1 s −1 of unstrained Ca GaI to 568.48 cm 2 V −1 s −1 under +4% tensile strain, accompanying with a twofold enhanced hole mobility anisotropy. Si (111) is predicted as an ideal substrate for Ca-doped 2D β -Ga 2 O 3 film characterized by a high hole mobility along y- direction based on lattice mismatch evaluations. The direct tunable bandgap, the ultra-high hole mobility, the enhanced anisotropy and p-type conductivity highlight its significant potential for nanoscale electronic applications.