Magnetic field effects on the valence band of AlGaAs and InGaAsP parabolic quantum wells

The influence of the valence band structure on the optical properties of quantum wells with a parabolic potential, consisting of AlxGa1−xAs and In1−xGaxAsyP1−y alloys, is studied and compared. The distribution of photogenerated carriers over the parabolic potential is found to be responsible for specific selection rules: the recombination due to only odd-indexed confined levels is observed. The reason for this is the accumulation of photogenerated holes at the center of the parabolic potential, which results in interband electron-hole recombination occurring at the center of the parabolic quantum wells. Furthermore, a specific valence band structure is found to be responsible for the magnetic-field-induced change in the photoluminescence circular polarization. In particular, at a certain magnetic field, the hybridization of the states of a heavy hole and a light hole results in the intersection of Landau levels with different spins, which leads to the observed change in the circular polarization of photoluminescence. The processes of long-term spin relaxation of heavy holes in both studied parabolic quantum wells are demonstrated, and the corresponding times are obtained.