Abstract
The k·p method + envelope function combination used for semiconductor heterostructures is based on approximations dubious under some conditions. We directly compare 8-band k · p with pseudopotential results for [001] GaAs/AlAs superlattices and quantum wells with all k · p input parameters directly computed from bulk GaAs and AlAs pseudopotential bands. We find generally very good agreement for zone-center hole states within ∼ 200 meV of the GaAs valence band maximum, but i) systematic errors deeper in the valence band and ii) qualitative errors for even the lowest conduction bands with appreciable contributions from off-Γ zinc-blende states. We trace these errors to inadequate k·p description of bulk GaAs and AlAs band dispersion away from the zone center.