Electron-energy-loss rates inAlxGa1−xAs/GaAs heterostructures at low temperatures

We have measured the energy-loss rates of electrons in modulation-doped ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As/GaAs heterojunctions at low temperatures. At the temperatures of this experiment, the energy loss is due to acoustic-phonon scattering, mostly through the deformation-potential interaction. We describe a theory of the energy-loss rate to acoustic phonons, discuss the effects of static screening, and determine a value of the deformation-potential constant by matching the theory to our experimental data. We show how the temperature dependence of the energy-loss rate can be used to determine the effectiveness of screening. In agreement with previous studies, we find that an anomalously large deformation-potential constant of 16.0 or 11.5 eV, for the screened or unscreened theory, respectively, is necessary to explain the data. However, in contrast with previous studies, we do not interpret this result as indicating some error in previous measurements of the deformation potential in bulk GaAs. Rather, we suggest that it results from some inadequacy in the model used to represent acoustic-phonon scattering in heterojunctions, or from some additional scattering mechanism not present in bulk material.