Low-temperature energy relaxation inAlxGa1−xAs/GaAs heterojunctions

The total average energy-loss rate of a two-dimensional electron gas in an ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterojunction at low temperatures is calculated for various densities and lattice temperatures. We take into account the inelastic scattering mechanisms due to acoustic phonons via deformation potential and piezoelectric coupling, and low-energy phonon modes associated with the coupling of quasiparticle excitations to the LO phonons. At high-carrier densities we show that the inclusion of these new phonon modes can explain the experimental data of Manion et al. [Phys. Rev. B 35, 9203 (1987)] for the energy-loss rates at low temperatures without using an enhanced value of the deformation-potential constant.