Peak in the magnetic-field dependence of diffusion-induced thermopower forn-Bi-Sb semiconducting alloys

A peak is detected on the dependence of the diffusion-induced thermopower o n transverse magnetic field in degenerate semiconducting alloys n-Bi1-xSbx (0.07 less than or equal to x less than or equal to 0.15) doped with tellur ium donor impurity. The temperature gradient is directed along the bisector axis CI of the monocrystalline sample and the magnetic field is along the triad axis C-3. The electron spectrum of the Bi-Sb alloys under investigati on consists of three equivalent ellipsoids with distinctly different effect ive masses along the axes of the ellipsoid (m parallel to/m perpendicular t o greater than or equal to 250). A simple kinetic theory shows that the pre sence of the peak on the diffusion thermopower is a manifestation of this s trong anisotropy in the electron spectrum and of the additive contribution of all three ellipsoids to electron transport. The nonmonotonic dependence of thermopower on the transverse magnetic field makes it possible to determ ine the electron relaxation time, while the temperature dependence of this relaxation time can be used to separate the relaxation time for electrons s cattered from ionized impurities and from acoustic phonons. (C) 2000 MAIK " Nauka/Interperiodica".