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A study of hydrogenic and metastable states of shallow-donor impurities in GaAs/GaAlAs multi-quantum wells

The energies of the excited states of a donor impurity in GaAs/GaAlAs multi-quantum wells are calculated using a model which is principally three-dimensional modified by the square well potential. Landau-like basis states are chosen and the effects of the Coulomb potential included using the techniques discussed by Simola and Virtamo (1978). The results are found to be in very good agreement with the authors earlier calculations, using an alternative method, for those states which are hydrogen-like in weak fields. However, additional states are also obtained that are not hydrogenic in nature. These states are commonly termed 'metastable', in that they only exist in strong fields. The predictions of the model are shown to be in good agreement with experimental data obtained previously in photoconductivity experiments.