Donor impurity states on structured semiconductor interfaces.

Abstract

Ground-state energies of shallow states of donor impurities on periodically structured interfaces formed by two semiconductors, such as GaAs/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As and Si/${\mathrm{SiO}}_{2}$ interfaces, are calculated variationally with the approximation that interfaces represent infinitely high potential barriers. The results show that the ground-state energies of the interface impurity states can be strongly affected by interface structures in GaAs/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As lateral surface superlattices produced by molecular-beam-epitaxy growth of AlAs/GaAs fractional-layer superlattices on [001] vicinal GaAs substrates and on ${\mathrm{SiO}}_{2}$/Si interfaces for Si with (001) orientation. The effects of the interface defects on the interface impurity states are negligible for Si/${\mathrm{SiO}}_{2}$ interfaces when the density of interface defects is less than ${10}^{10}$/${\mathrm{cm}}^{2}$.