Photoluminescence kinetics of indirect excitons in GaAs/AlxGa1-xAs coupledquantum wells

Photoluminescence (PL) kinetics of long-lifetime indirect excitons in a GaA s/AlxGa1-xAs coupled quantum well characterized by a small in-plane random potential was studied at temperatures 1.5 less than or equal to T less than or equal to 15 K for a wide range of exciton densities. Strong deviations of the indirect exciton PL kinetics from monoexponential PL rise/decay were observed at low temperatures and high exciton densities. In particular, ri ght after the excitation is switched off, the spectrally integrated indirec t exciton PL intensity increased sharply. Simultaneously, the indirect exci ton energy distribution was observed to narrow significantly. The observed increase in intensity is attributed to the sharp increase of occupation of the optically active exciton states. The energy distribution narrowing is e xplained in terms of the phonon mediated exciton energy relaxation in momen tum space and in the in-plane random potential. [S0163-1829(99)00104-6].