Optical absorption in semiconducting quantum-well structures: Indirect interband transitions

The optical absorption in semiconducting quantum-well structures is calculated for the case where the quantum well consists of an indirect-band-gap semiconductor. The absorption is obtained for the cases where the carriers are confined in either quasi-one- or quasi-two-dimensional structures. The absorption is found to be a nonmonotonic function of the photon energy for a fixed width of the quantum well. However, the exact behavior of the absorption due to interband transitions between the valence and conduction bands of the semiconductor is different for quasi-one- and quasi-two-dimensional structures reflecting the different behavior of the density of states for carriers confined in such quasi-one- and quasi-two-dimensional structures. Our results for quasi-one- and quasi-two-dimensional systems converge to each other in the appropriate limits and also to the results obtained for an indirect-band-gap semiconductor in the bulk limit.