Intersubband electron transitions due to electron-electron interactions inquantum-well structures

We have developed a full random-phase approximation formalism, and an effic ient computational scheme for calculating the electron-electron scattering rates in quantum wells in nonequilibrium steady state, including the full d ynamic screening. We apply our formalism to quantum-well systems studied in two recent experiments, which report different scattering rates for simila r structures and similar carrier densities, and obtain quantitative agreeme nt with both experiments. We show that the observed difference in the scatt ering rates is the result of different excitation levels in these experimen ts. We have also shown that the temperature dependence of the intersubband electron-electron scattering rate in one of the experiments is dominated by the higher-order, noncollective electron-electron scattering events at low temperature. We propose a scenario that could lead to the dominance of the electron-plasmon (collective) scattering processes. One of the experimenta l indications of this would be an activated temperature dependency of the i ntersubband electron-electron scattering rate.