Charged and neutral excitonic complexes in GaAs/AlGaAs quantum wells

The temperature and magnetic-field dependences of the recombination line of multiparticle excitonic complexes in undoped and lightly doped GaAs/AlGaAs quantum wells are investigated. These dependences have previously been attributed to free charged excitons (trions). It is shown that this line corresponds to a bound state of a complex, specifically, to an exciton bound on a neutral donor in a barrier. It is found that as the temperature or pump power is raised, there appear in the recombination spectrum not only a cyclotron replica shifted downward in energy but also a replica which is symmetrically shifted upwards in energy by an amount equal to the cyclotron energy and which is due to emission from an excited state of an impurity complex. The behavior of the cyclotron replicas is studied as a function of the electron density and temperature. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 730–735 (10 December 1997)