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 ξ separated by one monolayer steps across which the confining potential decreases by V0 for wider wells. A natural length is the localization length ξ0=πℎ/√ (2MV0) characterizing the minimum size island to confine an exciton. For small islands (ξ<ξ0), the absorption spectrum has a single exciton peak. As the island size ξ exceeds the localization length ξ0, the peak gradually splits into a doublet. Generally the spectra exhibit the following features: (1) the shape is very sensitive to ξ/ξ0 and depends only weakly on the ratio of island size to exciton radius; (2) in the small island regime ξ<ξ0, 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. copyright 1998 The American Physical Society