Donor impurity states on structured semiconductor interfaces

Ground-state energies of shallow states of donor impurities on periodically structured interfaces formed by two semiconductors, such as GaAs/Ga_1-x{Al}ₓ$As and Si/${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/Ga_1-x{Al}ₓ$As lateral surface superlattices produced by molecular-beam-epitaxy growth of AlAs/GaAs fractional-layer superlattices on [001] vicinal GaAs substrates and on ${SiO}₂$/Si interfaces for Si with (001) orientation. The effects of the interface defects on the interface impurity states are negligible for Si/${SiO}₂$ interfaces when the density of interface defects is less than ${10}¹⁰$/${cm}²$.