A donor-related resonance was observed in double-barrier resonant tunnelling devices when Si donors were incorporated into the quantum well. In high magnetic fields, this resonance predominated over the 1s resonance which was associated with the ground state of a single donor. The bias position of the donor resonance, its magnetic field dependence and its large amplitude, unambiguously indicated that the resonance was due to tunnelling through the ground state of a shallow donor with 2 bound electrons (D- level).

J.G.S.Lok, A.K.Geim, J.C.Maan, I.Marmorkos, F.M.Peeters, N.Mori, L.Eaves, T.J.Foster, P.C.Main, J.W.Sakai, M.Henini: Physical Review B, 1996, 53[15], 9554-7