Thermal diffusion temperature engineering leading to conduction type conversion in heterostructure films

Abstract

Knowledge of the complex phenomena underlying structural transitions is crucial for developing high performance solid-state materials. In this study, a thermal diffusion method is proposed to tune the conduction type of heterostructure films composed of combined n-type and p-type materials. The results reveal that the as-prepared films exhibit intrinsic n-type conduction in the lower BiSb layer. The exchange of Sb and Te atoms plays a pivotal role in the transition between n-type and p-type conduction. As Te diffuses into the Bi-Sb network structure, it replaces Sb and forms a p-type Bi₇Te₃ nanocrystalline phase, thereby shifting the conduction type of the films from n-type to p-type. Furthermore, the second-phase Bi₇Te₃ enhances the electrical conductivity of the ZnTe/BiSb heterostructure films, achieving 1.8 × 10⁵ S/m at 373 K. This study indicates that the thermal diffusion method is an effective approach for achieving the conversion between n-type and p-type conduction in heterostructure films.