Temperature dependence of the low-temperature mobility in ultrapure ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterojunctions: Acoustic-phonon scattering

The temperature dependence of the electron mobility in a high-mobility ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterojunction is theoretically investigated in the temperature range 4–40 K and in the electron-density range (0.3–6)×${10}^{11}$ ${\mathrm{cm}}^{\mathrm{-}2}$ by considering acoustic-phonon scattering. In agreement with recent experimental results, we find that the linear coefficient of the temperature dependence has a shallow minimum as a function of electron density. Our theoretical results support the claim of an enhanced value for the deformation-potential coupling in these systems, but not for the piezoelectric coupling.