Growth and Characterization of Epitaxial Bi(001)/PbTe(111) Hetero-structures for Thermionic Refrigeration

Metal/semiconductor multilayer structures are promising candidates for small-scale refrigeration and power-generation applications. In order to maximize the efficiency of such devices near room temperature, the semiconductor barrier material needs to have a small band gap, low thermal conductivity, and exhibit good epitaxy with respect to the metal layer. Metal/semiconductor hetero-junctions and multilayers of Bi(001)/PbTe(111), have been investigated in this study. Both structures were grown by molecular beam epitaxy. Ex-situ AFM results show that the morphology of the PbTe(111) layer is especially smooth over a micron length scale. Furthermore, for the first time, a PbTe(111)(√3x√3)R30^o surface reconstruction was observed with LEED. The quality of the pattern indicates long range order in the semiconductor film. Schottky barrier measurements on this metal/semiconductor hetero-junction and test results of a cooling device made of these structures will be reported. Supported by the ONR and by the DMS, U.S. DOE under contract No. DE-AC05-96OR22464 with LMER Corp.