The intervalley scattering in Bi and its influence on the transport properties at intermediate temperatures

In the range 77K<or=T<or=220K the mobilities in Bi have been calculated under the assumption that the scattering mechanism is intervalley scattering caused by optical and acoustical phonons for which the effective matrix elements have been found by Lopez (1968). For the electrons both the nonparabolic and the parabolic model are used. It is found that the acoustical phonon always gives results that are much larger than the measured mobilities, whereas the optical phonon gives results that agree very well with the measured values if one uses the nonparabolic model with the temperature-dependent band parameters found by Vecchi and Dresselhaus (1974). For the parabolic model the agreement is not so good. The thermopower is also calculated using the same scattering mechanism and the nonparabolic model. The result is that the thermopower for the electrons and the holes has the same sign (negative). The total thermopower is found to be nearly constant in the temperature range considered, but the values deviate by about 40% from the experimental values.