Optical studies of A+-centers in GaAs/AlGaAs quantum wells. Energy structure of the isolated centers, and their collective behavior

We report measurements of photoluminescence (PL) spectra due to A+-centers in GaAs/AlGaAs quantum well (QW). We observe temperature and pump dependence of the PL spectra as well as polarized PL spectra taken under an applied magnetic field and uniaxial stress. It was shown that hole–hole exchange interaction brings the A+-centers into a state characterized by J=2 split by QW potential in two states: ground mJ=0 and excited mJ=±1,±2 ones. Coulomb interaction changes the density of states (DOS) in the valence band thus a Coulomb gap appears. Our Monte-Carlo calculations of DOS demonstrate good agreement with the measured temperature PL dependence.