Magneto-optical study of excitonic states in In0.45Ga0.955As/GaAs multiplecoupled quantum wells

The excitonic states have been investigated in In(0.045)G(0.955)As/GaAs het erostructures consisting of i quantum wells (i=1,2,3,4) with 7.5 nm well th ickness. For a 2.5 nm barrier thickness between the wells, the electronic s tates are strongly coupled. Because of the coupling, the heavy-hole exciton nshh of each single quantum well is split into i(2) states. The states can be characterized according to their symmetry under a combination of the re flections of the single particles at the quantum-well plane. The energy ord er of the symmetric and antisymmetric states as a function of quantum-well number is investigated in detail, and compares well to the theoretical calc ulation. These coupled quantum-well structures exhibit somewhat three-dimen sional character based on the study of their exciton binding energies and w ave functions. Highly resolved photoluminescence excitation spectra are pre sented, measured in magnetic fields up to 13 T using circularly polarized l ight. Strong mixing between light- and heavy-hole excitons causes optical t ransitions into high-angular-momentum exciton states and strong anticrossin g effects. An anticrossing between the 3dhh(11) and hh(21) exciton is obser ved. Also, the light-hole exciton is found to possess Gamma(7g) and Gamma(6 g) symmetries.