Significantly Enhanced Thermal Conductivity of Supported MoS ₂ by Introducing Ga Vacancies in GaN Substrate

Generally, the interaction between substrate and two-dimensional (2D) materials significantly reduces the lattice thermal conductivity of 2D materials, thereby greatly affecting the heat dissipation performance of 2D material-based electronic devices. In this study, we demonstrate that the introduction of vacancies in the substrate can significantly enhance the lattice thermal conductivity of supported MoS2, achieving nearly twice the value compared to that on defect-free GaN substrate. Phonon modal analysis reveals that defect-free GaN substrate induces an avoided crossing region between the longitudinal acoustic (LA) and out-of-plane acoustic (ZA) branches of supported MoS2, indicating strong hybridization coupling between the LA and ZA phonon modes, largely suppressing the thermal conductivity of supported MoS2. Interestingly, the introduction of Ga vacancies in the substrate effectively decouples the hybridization interaction between the phonon modes, which consequently suppresses the three-phonon scattering process and prolongs the phonon lifetime, leading to significantly enhanced thermal conductivity of MoS2 supported on GaN substrate with Ga vacancies. Further analysis of the electron density distribution and interfacial interactions demonstrates that Ga vacancies in the GaN substrate modify the local bonding environment, and weaken the interaction between substrate and supported MoS2, thereby enhancing the thermal conductivity of supported MoS2. Our finding provides an effective strategy for enhancing heat transfer in supported 2D materials, offering promising prospects for heat dissipation in high-power electronic devices.