Phonon-drag thermoelectric power in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterojunctions at low temperatures

The phonon-drag thermoelectric power ${\mathit{S}}_{\mathit{g}}$ in ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterojunctions at low temperatures (≲5 K) is theoretically investigated based on the Cantrell-Butcher theory. The experimental data are well explained in terms of the deformation-potential constant D=8 eV without screening and the piezoelectric tensor ${\mathit{h}}_{14}$=1.2×${10}^7$ V/cm with screening. Above choice of parameters and treatment of screening for electron–acoustic-phonon scatterings are consistent with the analysis of the mobilities and energy-loss rates of electrons in ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterojunctions.