Thermal conductivity for III-V and II-VI semiconductor wurtzite and zinc-blende polytypes: The role of anharmonicity and phase space

© 2019 American Physical Society. We calculate the lattice thermal conductivity (κ) for cubic (zinc-blende) and hexagonal (wurtzite) phases for eight semiconductors using ab initio calculations and solving the phonon Boltzmann transport equation, explaining the different behavior of the ratio κhex/κcub between the two phases. We show that this behavior depends on the relative importance of two antagonistic factors: anharmonicity, which we find to be always higher in the cubic phase, and the accessible phase space, which is higher for the less symmetric hexagonal phase. Based on that, we develop a method that predicts the most conducting phase - cubic or hexagonal - where other more heuristic approaches fail. We also present results for nanowires made of the same materials, showing the possibility to tune κhex/κcub over a wide range by modifying their diameter, thus making them attractive materials for complex phononic and thermoelectric applications and systems.