ABSTRACT
Ga and In chalcogenides such as Ga2Te3, In2Te3, and Ga2Se3 share the same crystal structure, namely a defect zinc-blende cubic crystal (space group: F-43m). Due to the valence mismatch between the cation and the anion, a third of the cation sites are structural vacancies; that is, the chemical formula A2B3 (A = Ga, In; B = Te, Se) can be written as A2VA1B3, where VA indicates a vacancy. šese vacancies are thought to be distributed with various states. šey are also expected to a¤ect the thermoelectric properties of Ga and In chalcogenides. By forming such vacancies in a crystal, a signi›cant reduction in the lattice thermal conductivity due to strong phonon−vacancy scattering was recently observed in InSbIn2Te3 solid solutions.1 še thermoelectric properties of Ga and In chalcogenides, including the electrical resistivity, the Seebeck coe´cient, and the mobility of In2Te3, have been investigated.2-4 še mobility of In2Te3 was found to be much smaller than those of isoelectronic binary compounds such as InSb and to be independent of temperature, which is probably due to the predominance of electron−vacancy scattering.2 Furthermore, the electrical conductivities of Zn and Cu-doped Ga2Te3 and In2Te3 were found to be almost independent of impurity concentrations.5 In addition to the thermoelectric properties, the optical properties of Ga2Te3 and In2Te3 single crystals6 and the dielectric and ac conductivity properties of as-grown Ga2Te3 crystals7 have been examined.
