The intrasubband and intersubband relaxation of nonequilibrium electron populations in wide semiconductor quantum wells

The evolution of nonequilibrium electron distributions in wide GaAs quantum wells, driven by electron–electron scattering processes, is calculated through numerical integration of the Boltzmann collision integrals, by incorporating the multi-subband dynamically screened Coulomb interaction derived in the random phase approximation. We present results for the thermalisation and intersubband population relaxation times of these distributions, for different carrier densities and lattice temperatures, and for different fractions of the population excited into the upper subband, including the highly nonequilibrium case of a population inversion between the subbands. We compare the relative importance of electron–electron and electron–LO-phonon scattering processes in determining the intersubband population relaxation times. The role played by screening in intersubband transitions is discussed.