Simple tuning of carrier type in topological insulator Bi2Se3 by Mn doping

Abstract

Bi2Te3 is a well-known thermoelectric material for room-temperature operations because it has a high Seebeck coefficient, and the charge carrier type is easily tunable. However, the carrier type of Bi2Se3 is not tunable, which is one of the weaknesses for the thermoelectric applications, in spite of its high Seebeck coefficient. Here, we report the tuning of charge carriers in Bi2Te3 from n type to p type by doping Mn into the Bi sites. The carrier type is n type up to the Mn doping level of 5% and changes to p type above 5% Mn doping. The temperature-dependent resistivity of Bi2−xMnxSe3 shows a metallic behavior for x < 0.05, while for x ≥ 0.05, it shows an upturn at low temperatures. This provides evidence that by Mn doping, the Fermi level is continuously tuned from the bulk conduction band to the bulk valence band. The Seebeck coefficient increases monotonically with increasing temperature, and the absolute values are same for both n- and p-type samples. This implies that Bi2Se3 is another candidate of high-temperature thermoelectric materials, like Bi2Te3, simply by Mn doping.