The phonon-drag contribution to the thermoelectric power is calculated at low temperatures in polar semiconductor heterostructures. Carries are assumed to interact with longitudinal acoustic phonons through deformation potential and with both longitudinal and transverse acoustic phonons through piezoelectric field. The magnitude and the temperature dependence of the phonon-drag contribution calculated without any adjustable parameter agree reasonably well with recent data from $\frac{{\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}}{\mathrm{Ga}\mathrm{As}}$ heterolayer. Both piezoelectric scattering and deformatin potential scattering yield comparable contributions in the temperature range studied (i.e., below 10 K), although the former (latter) contribution becomes more important below (above) 3-4 K. Dielectric screening is found to reduce the phonon-drag thermopower significantly.

• Received 3 June 1988

DOI:https://doi.org/10.1103/PhysRevB.38.6345