High figure of merit ZT in PbTe and Bi/sub 2/Te/sub 3/ based superlattice structures by thermal conductivity reduction

In superlattice (SL) structures an enhancement of the thermoelectric figure of merit ZT compared to homogeneous materials can be achieved by reduction of the thermal conductivity /spl lambda/. In this context thermoelectric properties of PbTe/ PbSe/sub x/Te/sub 1-x/-SL's, and PbTe(BaF/sub 2/) doping superlattices (SL), and of Bi/sub 2/(Se/sub x/Te/sub 1-x/)/sub 3//Bi/sub 2/(Se/sub y/Te/sub 1-y/)/sub 3/-SL structures are presented. All samples were grown on BaF/sub 2/[111]-substrates by molecular beam epitaxy (MBE). A significant reduction of the in-plane thermal conductivity /spl lambda/ compared to corresponding bulk materials was observed. As the power factors are only slightly reduced, a net increase of the figure of merit ZT can be calculated. The temperature dependence of ZT is discussed.