Spatial correlations and temperature dependence of the phonon-assisted hopping thermoelectric power in amorphous semiconductors

The assumption that the thermoelectric power of amorphous elemental semiconductors remains constant (in the hopping regime) down to zero temperature (which accords with some experiments on e.g. amorphous Ge performed above 100 K) is shown to be incompatible with the lowest order single-phonon hopping theory until the spatial interlevel correlations are taken into account.