Radiative behavior of negatively charged excitons in CdTe-based quantum wells: A spectral and temporal analysis

Using reflectivity and picosecond time-resolved photoluminescence, we have studied the intrinsic optical properties of negatively charged excitons in modulation doped CdTe quantum wells. In emission, we observe simultaneously a low energy exponential tail in the charged exciton spectral line and a l inear increase of its radiative lifetime with temperature. In absorption, w e find a consistent decrease of the charged exciton oscillator strength wit h temperature. For low electron concentrations these observations are well reproduced by a model of delocalized and thermalized three-particle complex es. The model takes into account the recoil momentum of the electron during the charged exciton optical transition. It is further found to compare wel l with lifetime measurements up to high carrier concentrations. Small devia tions from the theoretical predictions occur only below 7 K due to localiza tion effects and for the highest carrier concentration of n(e)similar to2 x 10(11) cm(-2).