Heterolayer mobility in the Bloch-Grüneisen range

It is shown that, for two-dimensional heterolayer conduction at low temperatures, the phonon-scattering contribution to the reciprocal of the ohmic mobility has a Bloch-Grüneisen regime, for low enough temperatures T, in which the deformation coupling gives a term proportional to T⁷ and (for polar semiconductors) piezoelectric coupling gives a term proportional to T⁵. It is pointed out that there could be an intermediate temperature range with a slower T dependence.