Dynamical properties of trions and excitons in modulation doped CdTe/CdMgZnTe quantum wells

We report on the population and phase relaxation of neutral excitons (X) an d positively charged excitons (X+), called trions, in p modulation doped Cd Te/CdMgZnTe multiple quantum wells. Time-resolved photoluminescence (PL) me asurements which investigate the population dynamics show that trions and e xcitons are in thermal equilibrium with each other and allow to determine t hr lifetimes of trions and excitons. The coherent dephasing of both quasipa rticles is studied by degenerate four-wave mixing (FWM). The slower dephasi ng of trions compared with excitons is interpreted in terms of trion and ho le localization, Under excitation with spectrally broad femtosecond laser p ulses, the FWM traces show modulations due to quantum beats between the tri on and exciton transitions. (C) 1998 Elsevier Science S.A. All rights reser ved.