Electronic structures of GdAs/GaAs superlattices

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Abstract
Electronic structures of semimetal-semiconductor superlattices made of GdAs and GaAs are studied by a second-neighbor tight-binding model. It is found that this semimetal-semiconductor superlattice is metallic with overlapping conduction and valence bands for GdAs layers as thin as two monolayers. This is in qualitative agreement with recent experimental observation. The superlattice states with energies near the Fermi surface consist of states derived from the GdAs valence bands and the lowest GdAs conduction bands with wave vectors near point X. It is shown that the two types of superlattice energy bands can be simulated by a more sophisticated effective-mass theory with anisotropic, energy-dependent effective masses.