CHARGED AND NEUTRAL EXCITONIC COMPLEXES IN GAAS ALGAAS QUANTUM-WELLS/

The temperature and magnetic-field dependences of the recombination li ne of multiparticle excitonic complexes in undoped and lightly doped G aAs/AlGaAs quantum wells are investigated. These dependences have prev iously 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 tha t as the temperature or pump power is raised, there appear in the reco mbination spectrum not only a cyclotron replica shifted downward in en ergy but also a replica which is symmetrically shifted upwards in ener gy by an amount equal to the cyclotron energy and which is due to emis sion from an excited state of an impurity complex. The behavior of the cyclotron replicas is studied as a function of the electron density a nd temperature. (C) 1997 American Institute of Physics.