THEORY OF ASYMMETRIC BROADENING AND SHIFT OF EXCITONS IN QUANTUM STRUCTURES WITH ROUGH INTERFACES

A quantum-mechanical theory of the influence of disorder on the motion of free particles is presented. Taking into account the dominant pair correlations of the potential fluctuations an analytical formula is derived for the asymmetrically broadened and shifted spectral function. The results are in agreement with a complete numerical treatment of disorder. The theory is applied to excitons in quantum wells with rough interfaces. We show that mainly the center-of-mass motion is influenced. Both the effect of the correlation and the strength of the accompanying potential fluctuations on the optical absorption are discussed. We clarify the relationship between the asymmetry, the shift, and the width of exciton lines. In the limit that these effects are only due to static interface disorder, an analytical relation between potential strength and correlation length is suggested.