Exciton localization by potential fluctuations at the interface of InGaAs/GaAs quantum wells

Photoluminescence measurements in InGaAs/GaAs quantum wells, both doped and undoped, have provided evidence of a bound exciton of intrinsic origin with peculiar properties. The intensity of this bound exciton exhibits an unusual dependence on the exciting power density. Its relative strength with respect to the free exciton is strongly modified by small changes of the excitation wavelength. Its linewidth closely matches that measured for the heavy-hole free exciton, independent of well width and indium concentration. These features lead one to conclude that the intrinsic bound exciton is localized by a photoassisted interfacial roughness. Possible microscopic origins of such a localizing potential are also tentatively given.