THERMOELECTRIC PROPERTIES OF CUIN1-XGAXTE2 SINGLE-CRYSTALS

In this paper we report on crystal growth and the electrical character ization of the compounds CuGaTe2, CuInTe2 and their solid solutions Cu In1-xGaxTe2. Single crystals were obtained by zone melting and a verti cal Bridgman technique. From resistivity and Hall effect measurements in the temperature range of 35 to 400 K the carrier concentrations and mobilities were determined. All samples showed p-type conductivity. T he hole densities at room temperature were approximately p = 10(20) cm (-3), which indicates that these materials are degenerate semiconducto rs. For thermoelectric applications weakly degenerate semiconductors a re required. Ln order to investigate whether these materials are suita ble for thermoelectric applications we measured the Seebeck coefficien t between 90 and 100 K and the thermal conductivity in the range of 80 to 300 K. From the analysis of the obtained data we were able to calc ulate the temperature dependence of tile Fermi level, the density-of-s tates effective mass of holes, thc electronic contribution to the ther mal conductivity and the figure of merit for a thermoelectric material . With a theoretical estimation it is shown that there is a optimum do ping concentration which leads to a maximum figure of merit Z for this material group. Further possibilities to improve Z are discussed.