Anticrossing and coupling of light-hole and heavy-hole states in (001) GaAs/AlxGa1-xAs heterostructures

Heterostructures sharing a common atom such as AlAs/GaAs/AlAs have a D-2d point-group symmetry which allows the bulk-forbidden coupling between odd-parity light-hole states (e.g., lh1) and even-parity heavy-hole states (e.g., hh2). Continuum models, such as the commonly implemented (standard model) k.p theory miss the correct D-2d symmetry and thus produce zero coupling at the zone center. We have used the atomistic empirical pseudopotential theory to study the lh1-hh2 coupling in (001) superlattices and quantum wells of GaAs/AlxGa1-xAs. By varying the Al concentration x of the barrier we scan a range of valence-band barrier heights DeltaE(v)(x). We find the following: (i) The lh1 and hh2 states anticross at rather large quantum wells width or superlattice periods 60