Splitting of the excitonic peak in quantum wells with interfacial roughness

Excitons in a quantum well depend on the interfacial roughness resulting from its growth. The interface is characterized by islands of size xi separated by one monolayer steps across which the confining potential decreases by V-0 for wider wells. A natural length is the localization length xi(0) = pi h/ root 1MV(0) characterizing the minimum size island to confine an exciton. For small islands (xi<xi(0)), the absorption spectrum has a single exciton peak. As the island size xi exceeds the localization length xi(0), the peak gradually splits into a doublet. Generally the spectra exhibit the following features: (I) the shape is very sensitive to xi/xi(0) and depends only weakly on the ratio of island size to exciton radius: (2) in the small island regime xi<<xi(0), the asymmetric shape of the exciton peak is correctly described by a model of white-noise potential, except for the position of the peak which still depends on the correlation length of the disorder. [S0163-1829(98)06348-6].