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 j separated by one monolayer steps across which the confining potential decreases by V0 for wider wells. A natural length is the localization length j05p\/A2MV0 characterizing the minimum size island to confine an exciton. For small islands (j,j0), the absorption spectrum has a single exciton peak. As the island size j exceeds the localization length j0 , the peak gradually splits into a doublet. Generally the spectra exhibit the following features: ~1! the shape is very sensitive to j/j0 and depends only weakly on the ratio of island size to exciton radius; ~2! in the small island regime j!j0 , 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#