Temperature dependent dephasing of excitons and trions in a ZnMgSe/ZnSe single quantum well

We investigate the dephasing of excitons and negatively charged excitons (t rions) in ZnSe/Zn0.9Mg0.1Se single quantum wells by temperature dependent s pectrally resolved transient four-wave mixing. The trion transition shows a binding energy of 3 meV and is discriminated from the biexciton by its tem perature dependence. The measurements exhibit a significant enhancement of the exciton dephasing at low temperatures due to the presence of incoherent electrons which are optically excited from the GaAs substrate and captured by the quantum well. With rising temperature the accumulated electron dens ity is reduced due to thermal activation leading to a significant decrease of the exciton homogeneous linewidth.