Native Defect Engineering in CuInTe₂

Abstract

Ternary diamond-like semiconductors, such as CuInTe2, are known to exhibit promising p-type thermoelectric performance. However, the interplay between growth conditions, native defects, and thermoelectric properties have limited their realization. First-principles calculations of CuInTe2 indicate that the electronic properties are controlled by three dominant defects: VCu, CuIn, and InCu. The combination of these low-energy defects with significant elemental chemical potential phase space for CuInTe2 yields a broad phase width. To validate these calculations, polycrystalline, bulk samples were prepared and characterized for their structural and thermoelectric properties as a function of stoichiometry. Collectively, the off-stoichiometric samples show a range of carrier concentrations that span 5 orders of magnitude (1015 to 1019 h+ cm–3). Mobility of the off-stoichiometric samples suggests that copper vacancies act as strongly scattering point-defect sites, while the other native defects scatter less strongly. Such vacancy scattering extends to the thermal conductivity where a reduction in κL is observed and contributes to enhanced thermoelectric performance. Understanding and controlling the native defects in CuInTe2 provides a route toward n-type dopability as well as rational optimization of the p-type material.