DOUBLET STRUCTURES IN QUANTUM-WELL ABSORPTION-SPECTRA DUE TO FANO-RELATED INTERFERENCE

In this theoretical investigation we predict an unusual interaction be tween a discrete state and a continuum of states, which is closely rel ated to the case of Fano interference. It occurs in a GaAs/AlxGa1-xAs quantum well between the lowest light-hole exciton and the continuum o f the second heavy-hole exciton. Unlike the typical case for Fano reso nance, the discrete state here is outside the continuum; we use uniaxi al stress to tune its position with respect to the onset of the contin uum. State-of-the-art calculations of absorption spectra show that as the discrete state approaches the continuum, a doublet structure forms that reveals anticrossing behavior. The minimum separation energy of the anticrossing depends characteristically on the well width and is u nusually large for narrow wells. This offers striking evidence for the strong underlying valence-band mixing. Moreover, it proves that previ ous explanations of similar doublets in experimental data, employing s imple two-state models, are incomplete.