Hot photoluminescence in quantum-well structures under continuous wave pumping

Recent results on recombination photoluminescence of hot electrons and electron-hole pairs in quantum wells of the GaAs/AlGaAs type are discussed. It is shown that linear polarization of hot photoluminescence is due to the optical alignment of two-dimensional (2D) electron momenta by linearly polarized light. The times of intra- and intersubband scattering of 2D electrons were determined from hot luminescence depolarization in a magnetic field. The intrasubband scattering times are found to be close to 150 fs for the well widths from 50 to 100 AA. This agrees with a calculation based on the assumption that 2D electrons are scattered by bulk phonons, which is consistent with a prediction from a dielectric continuum model. Experimental dispersion dependences in the valence subbands of quantum wells were first obtained from the hot photoluminescence spectra. In a perpendicular magnetic field, which restricts hot carrier motion in the quantum-well planes, radiation flares up due to recombination of hot electrons and holes created by the same light quantum (geminate recombination). Its spectral and polarization properties depend noticeably on the magnetic field and initial energy of hot carriers.