Magnetotransport properties at Low-temperature of Thallium doped PbTe grown by Molecular Beam Epitaxy.

We have grown PbTe thin films, of various thicknesses, on single crystal CdTe(211)B substrates by Molecular Beam Epitaxy. PbTe is a narrow gap semiconductor that crystallizes in the rock-salt structure. PbTe is an important thermoelectric material with figure of merit (ZT) exceeding 2.0. The films are doped with Thallium (Tl) acting as an acceptor, the only impurity known to cause superconductivity in PbTe, even though it can be doped with other impurities to similar carrier concentrations levels. We investigate the low temperature magnetotransport properties of PbTe films doped Tl. We find evidence of a Kondo effect below 15K for high Tl doping with hole carrier concentrations ranging from 10¹⁴ to 10¹⁵ cm^-2.