Inter-subband relaxation due to electron–electron scattering in quantum well structures

We present a full RPA formalism, and an efficient computational scheme for the inter-subband relaxation processes due to the electron–electron interactions in quantum well structures. Based on a full self-energy calculation, our formalism includes both single particle (e.g. Auger) and collective (plasmon) processes, and is applicable to strongly inhomogeneous, non-equilibrium steady-state systems. To show the efficacy of our formalism, we analyze two recent experiments which report different scattering rates for similar structures and similar carrier densities. We obtain quantitative agreement with the experimental results, showing that the observed difference is due to different excitation levels of the electron population. We have also shown, that the electron–plasmon scattering dominates inter-subband electron–electron scattering at low temperatures.