EXCITONS AND EXCITONIC COMPLEXES IN GAAS ALGAAS QUANTUM-WELLS WITH A LOW-DENSITY QUASI-2-DIMENSIONAL ELECTRON AND HOLE CHANNEL/

The recombination spectra of excitons and excitonic complexes in undop ed GaAs/AlGaAs single quantum wells are investigated. It is shown on t he basis of a study of the magnetic-field dependence of the emission s pectra and the degree of optical orientation in zero magnetic field an d on the basis of electrooptic measurements that not only the density but also the sign of the charge carriers in a well depend strongly on the photoexcitation energy. It is shown on the basis of a comparative analysis of the spin splitting of the recombination lines of free and bound excitons that the recombination line which was attributed earlie r to a positively charged exciton corresponds to the recombination of an exciton bound on a neutral acceptor. (C) 1998 American Institute of Physics. [S0021-3640(98)01909-4].