AbstractWe investigated high density excitation effects in propagation and diffusion processes of free excitons confined in an Lz‐gradient GaAs quantum well (QW). From measurements of µPL spectra, it was found that driving force owing to a confined‐energy gradient makes QW excitons propagate asymmetrically to the falling gradient direction. In addition, it was figured out that many body interactions among the high density QW excitons enhance their isotropic diffusion process in the Lz‐gradient QW (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)