N doping has emerged as a promising approach to achieving $p$-type conductivity in $\beta \text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$, a leading ultrawide band gap semiconductor for high-power electronics. However, its impact on thermal transport remains insufficiently understood. In this study, we systematically investigate the effect of N substitution at three crystallographically distinct O sites, denoted as ${\mathrm{O}}_{\mathrm{I}}, {\mathrm{O}}_{\mathrm{II}}$, and ${\mathrm{O}}_{\mathrm{III}}$, in modifying phonon transport behaviors in $\beta \text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$. The first-principles calculations combined with atomistic Green's function and Boltzmann transport theory reveal that N doping induces a local ionic-to-covalent bonding transition, characterized by enhanced orbital hybridization, reduced Bader charge transfer, and asymmetric electron delocalization. This transition perturbs local interatomic force constants and enhances lattice anharmonicity, with its intensity strongly dependent on the specific doping site. Moreover, substitution at the ${\mathrm{O}}_{\mathrm{II}}$ site, located within a distorted $\mathrm{G}{\mathrm{a}}_4\mathrm{O}$ tetrahedron, exhibits the most pronounced bonding transition, resulting in stronger phonon localization and enhanced phonon-defect scattering <10 THz. Consequently, the thermal conductivity is significantly reduced, particularly along the $b$ axis, with suppressions of up to 40% at a doping concentration of $1\times {10}^{20}\mathrm{c}{\mathrm{m}}^{-3}$, relevant for ohmic contacts in transistors. In contrast, doping at the ${\mathrm{O}}_{\mathrm{I}}$ site yields minimal disruption to bonding and heat conduction. These findings indicate the importance of doping-site selectivity in modulating phonon transport via local bonding effects and providing insights for thermal management in $\beta \text{−}\mathrm{G}{\mathrm{a}}_2{\mathrm{O}}_3$-based devices.

Close

PrevNext

View figure in article

• Phonons
• Thermal conductivity
• Doped semiconductors
• Boltzmann theory
• Density functional calculations