Relaxation dynamics of microcavity polaritons in the presence of an electron gas

The dynamics of microcavity polaritons in the presence of an electron gas is investigated by means of time-resolved photoluminescence. The electrons induce a strong acceleration of the population build-up and decay, both in large wave-vector states (reservoir) and at the center of the Brillouin zone. We show that the dynamic changes in the reservoir are due to a better exciton relaxation and to the formation of a thermalized trion population. The population of the polariton states close to the center of the Brillouin zone adiabatically follows the reservoir population.