HALL-EFFECT MEASUREMENTS ON GALLIUM-SULPHIDE SINGLE CRYSTALS

On n- and p-type GaS, Hall-effect measurements were carried out in a temperature range of (80÷600) °K, at the higher temperatures in the dark as well as under illumination. At the lower temperatures only photo-Hall effect could be measured because of the high dark resistance of the samples. The Hall mobility (magnetic field perpendicular to the layers) can be expressed as μ H=12(T/T 0)-2.4 cm2 V-1 s-1 for holes and μ H=16(T/T 0)-2.4 cm2 V-1 s-1 for electrons, T 0=300 °K. An interpretation of these results with a scattering theory of Fivaz and Mooser yields a phonon energy of 0.05 eV. From infra-red-absorption measurements a fundamental peak is found at 0.04 eV; according to theoretical expectations this i.r. value should be smaller than 0.05 eV. Weak coupling of the carriers with the lattice as required by theory leads to m e* > 1.5 m 0 and m h* > 2 m. Thermoelectric power measurements carried out on n-type crystals by Kipperman and Sliepenbeek indicated m e* = 5 m 0. © 1969 Società Italiana di Fisica.