Crystal structures and stabilities of InxGa1-xN and Mg-doped InxGa1-xN: A first-principles calculation

The ground-state configurations and electronic characteristics of InGaN crystals with varying In compositions and their p-type doped counterparts were investigated. A first-principles computational framework was implemented in CASTEP, with its reliability validated through direct comparison with prior experimental data. The calculations demonstrate that the structural stabilities of In_xGa_1-xN and In_xGa_1-xN:Mg crystals are predominantly governed by the type of constituent atoms, while lattice site occupancy exerts relatively minor influence on structural stability.‌ Bonding mechanisms of In_xGa_1-xN and In_xGa_1-xN:Mg crystals were revealed and analyzed, finding that these heteronuclear bonds predominantly arise from orbital hybridization between metal sp-states and nitrogen p-states. Furthermore, it is revealed that the decreasing stability with increasing In content originates from a twofold mechanism: a chemical substitution effect and a universal “expansion effect” caused by lattice strain. This work provides a fundamental explanation for the instability of In-rich nitrides, offering a theoretical foundation for the design of optoelectronic devices.