title: Thermal Conductivity of Wurtzite Zinc-Oxide from First-Principles Lattice Dynamics--a Comparative Study with Gallium Nitride.
abstract: Wurtzite Zinc-Oxide (w-ZnO) is a wide bandgap semiconductor that holds promise in power electronics applications, where heat dissipation is of critical importance. However, large discrepancies exist in the literature on the thermal conductivity of w-ZnO. In this paper, we determine the thermal conductivity of w-ZnO using first-principles lattice dynamics and compare it to that of wurtzite Gallium-Nitride (w-GaN)--another important wide bandgap semiconductor with the same crystal structure and similar atomic masses as w-ZnO. However, the thermal conductivity values show large differences (400 W/mK of w-GaN vs. 50 W/mK of w-ZnO at room temperature). It is found that the much lower thermal conductivity of ZnO originates from the smaller phonon group velocities, larger three-phonon scattering phase space and larger anharmonicity. Compared to w-GaN, w-ZnO has a smaller frequency gap in phonon dispersion, which is responsible for the stronger anharmonic phonon scattering, and the weaker interatomic bonds in w-ZnO leads to smaller phonon group velocities. The thermal conductivity of w-ZnO also shows strong size effect with nano-sized grains or structures. The results from this work help identify the cause of large discrepancies in w-ZnO thermal conductivity and will provide in-depth understanding of phonon dynamics for the design of w-ZnO-based electronics.
authors.affiliation: Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46530.
authors.forename: Xufei
authors.initials: X
authors.lastname: Wu
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433.|Universal Technology Corporation, Dayton, OH, 45342.
authors.forename: Jonghoon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433.|Universal Technology Corporation, Dayton, OH, 45342.
authors.forename: Vikas
authors.initials: V
authors.lastname: Varshney
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433.|Universal Technology Corporation, Dayton, OH, 45342.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Wohlwend
authors.affiliation: Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433.
authors.forename: Ajit K
authors.initials: AK
authors.lastname: Roy
authors.affiliation: Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46530.|Center for Sustainable Energy at Notre Dame, Notre Dame, IN 46530.
authors.forename: Tengfei
authors.initials: T
authors.lastname: Luo