Electronic Raman scattering from weakly bound electrons in lightly doped n-type GaAs

We have examined the physical properties of donor bound electrons in a series of very lightly doped n-type GaAs samples (doped with 2x10(14)-3x10(15) Te atoms/cm(3)) being far-infrared and inelastic light scattering measurements at low temperature. In this system there is a pronounced coupling between the spins of nuclei and donor electrons, which would be suitable for application in the quantum computer envisaged by Kane. The infrared and Raman results reveal correspondingly the 1s-2p(+/-) and 1s-2s transitions of the weakly bound donor at around 40 cm(-1). The Raman results are remarkable for the intensity of the scattering owing to excitonic resonance enhancement. An impurity-induced, localized phonon was observed at 271.7 cm(-1), again owing to strong resonance enhancement of the Raman cross section.