Energy relaxation in GaAs/AlGaAs two-dimensional structures

Results on energy relaxation in low carrier concentration two-dimensional structures over the lattice temperatures, Tl, of 3 K to 150 K are presented. The power loss per carrier as a function of electron temperature, Te, was experimentally determined using the mobility-field, mobility-temperature thermometric technique. In the acoustic phonon regime, below about Tl=20 K, the power loss per carrier was found to be proportional to Te-Tl. Theoretical calculations in this temperature regime predict a similar form but do not agree in magnitude. Above Tl=40 K the power loss per carrier was modelled using an optic phonon scattering model, which includes the effects of hot phonons, and which predicts a phonon lifetime of 11 ps+or-1 ps. Between these two regimes, for the multi-quantum well, the experimental power loss was found to be greater than the theoretical power loss. This discrepancy has been explained by invoking scattering due to optic phonon-plasmon coupling. Using the optic phonon-plasmon coupled mode energy and the scattering time as fitting parameters values of 10 meV for the energy of the coupled mode and 400 ps for the scattering time were obtained.