Binding energy of the exciton–ionized-donor complex with the donor on the surface of a nonpolar semiconductor

The exciton–ionized-donor complex with the donor on the surface of a semiconductor (X,${\mathit{D}}^{+}$ ${)}_{\mathit{s}}$ is investigated. The binding energy of the complex is calculated variationally as a function of the effective-mass ratio σ of the electron to the hole, and high-frequency dielectric constant ${\mathrm{\epsilon }}_{\mathrm{\infty }}$ of the host semiconductor occupying the semi-infinite space. No unstable range of σ appears.