Self-compensation induced vacancies for significant phonon scattering in InSb

Phonon scattering by point defects via mass differences and strain fluctuations could effectively reduce the lattice thermal conductivity. The atomic mass difference can be maximized by introducing the vacancies thus leading to a significant phonon scattering. Usually, the vacancies are introduced by tuning the stoichiometry or forming solid solution with certain compound that contains intrinsically high concentration of vacancies. In this work, we demonstrate that vacancies can be effectively induced by the self-compensation effect via chemical doping. Indium (In) vacancies in InSb were induced by Te-doping and a substantial reduction in thermal conductivity was observed. Room temperature lattice thermal conductivity of the melted and then hot-pressed InSb (without In vacancies) is ~ 14.5 W m⁻¹ K⁻¹ but only ~ 3.8 W m⁻¹ K⁻¹ for InSb_0.96Te_0.04 (with In vacancies), a reduction of ~ 74%. The advantage of using this strategy for phonon engineering lies in the fact that a substantial reduction in thermal conductivity can be achieved even when the dopant concentration is rather low. Since the self-compensation effect is widely observed in different compounds, it indicates that the vacancy engineering strategy used here is also applicable to a variety of other materials to effectively reduce the lattice thermal conductivity.