LOCALIZATION OF EXCITONS IN THERMALLY ANNEALED IN0.14GA0.86AS GAAS QUANTUM-WELLS STUDIED BY TIME-INTEGRATED 4-WAVE-MIXING/

We have studied the effects of thermal annealing on the localization o f excitons in In0.14Ga0.86As/GaAs multiple quantum wells by means of l inear spectroscopy and time-integrated four-wave mixing. The localizat ion occurs due to interface roughness resulting from well width fluctu ations, respectively, alloy fluctuations on a length scale comparable to the exciton Bohr radius. Due to lateral inhomogeneities of the diff usion of In out of the quantum well and of Ga into the quantum well du ring the annealing, we observe a structural transition of the localiza tion potential for annealing temperatures greater than 850 degrees C. This transition is characterized by the development of disorder on a l ength scale larger than the exciton Bohr radius.