THERMOPOWER AND CONDUCTIVITY OF INAS GASB CROSSED-GAP HETEROSTRUCTURES IN A MAGNETIC-FIELD/

The transport properties of InAs/GaSb crossed-gap heterostructures are relatively complex because of the presence of nearly equal areal dens ities of electrons and holes at the interfaces. We have made a compreh ensive study of the independent components of both the resistivity and thermopower tensors in the temperature range 0.3-5 K in perpendicular magnetic fields where semiclassical effects are dominant. It is shown that the results are best analyzed and understood in terms of the con ductivity cr and thermoelectric epsilon tensors, The data are consiste nt with the assumption that the electron and hole gases make independe nt and additive contributions to sigma and epsilon, and that these con tributions are easily separated. The thermopower is dominated by phono n drag above similar to 1 K, and the individual contributions of the e lectrons and holes are similar in temperature and field dependence to those observed in GaAs/Ga1-xAlxAs heterojunctions with only one carrie r type present, though the absolute magnitudes are smaller.