Tight-binding approach to excitons bound to monolayer impurity planes: Strong radiative properties of InAs in GaAs

A theory of Wannier-Mott excitons bound to monolayer (ML) impurity planes in semiconductors, which is based on Green's function tight-binding calculations of the single-particle states, is presented. Binding energies and oscillator strengths for one and two MLs of InAs in GaAs are predicted to be much larger than in the usual InxGa1-xAs/GaAs thick quantum wells. The reason is the increase of effective mass of both carriers due to folding of the InAs bands along the growth direction. The results suggest that ML insertions can be used as intense light sources in light-emitting devices.