On boundary condition-induced states in low-dimensional semiconductor structures

We examine different solutions of multi-band k(.)p Hamiltonians. We refer m ainly to the "intrinsic surface states", with energies in the forbidden ene rgy gap, that were proposed recently (Sercel et al. Phys. Rev. Lett. 83 (19 99) 2394) for bare and capped nanocrystals. We review analytical and numeri cal results for different Hamiltonians and demonstrate that spurious soluti ons occur both for quantum dots and quantum wells. By showing peculiar char acteristics of the proposed gap states, we argue that they are spurious sol utions appearing in multi-band formulations due to infinite potential barri er imposed at the nanocrystal surface. We propose that these states are not physical and should be excluded from the theoretical interpretation of exp erimental data. (C) 2001 Elsevier Science Ltd. All rights reserved.