Radiative lifetime of negative trions in GaAs and CdTe quantum wells

We have studied experimentally the radiative lifetimes of negatively charge d excitons (X-) and neutral excitons (X) in GaAs and CdTe quantum wells. De spite the different optical properties (e.g. trion binding energies) and th e different quantum well structures of the studied samples, we find quite s imilar X- lifetimes in the range of 45 to 60 ps. On the other side, the X l ifetimes are very different and influenced by the material. For relatively low electron concentrations, the X- lifetime is found to be constant with i ncreasing temperature in a given range. This time behaviour of X- suggests that X- is localised for low electron concentrations in the CdTe QW.