  We analyze the tunnel coupling between an impurity state located in a
$\delta$-layer and the 2D delocalized states in the quantum well (QW) located
at a few nanometers from the $\delta$ -- layer. The problem is formulated in
terms of Anderson-Fano model as configuration interaction between the carrier
bound state at the impurity and the continuum of delocalized states in the QW.
An effect of this interaction on the interband optical transitions in the QW is
analyzed. The results are discussed regarding the series of experiments on the
GaAs structures with a $\delta$-Mn layer.
