EFFECTIVE EXCITON MOBILITY EDGE IN NARROW QUANTUM-WELLS

An effective mobility edge for excitons in two-dimensional systems is shown to exist by comparing photoluminescence (PL) and PL excitation ( PLE) with excitation-energy-dependent micro-FL spectra. The effective mobility edge of excitons shifts towards higher energies with increasi ng potential fluctuations. This blue shift is correlated with a sharp decrease of the PLE signal resulting in an extremely large energy sepa ration between the PL and PLE spectra. Numerical simulations using a r andom potential confirm these results and predict a significant deviat ion of the PLE from the absorption spectrum.