Abstract
The effects of tensile strain on the energy-band structures of semiconductor quantum wells and superlattices (SL’s) are studied theoretically, with emphasis on structures with unique valence-subband configurations achievable only through the use of tensile strain. Quantum wells are treated using finite-element envelope-function calculations which fully treat interactions between the light-hole, heavy-hole, and split-off valence bands, whereas strained SL’s are modeled using a superlattice K⋅p approach modified to treat strain effects. The two models are described in detail, tested for appropriate cases where both models should be applicable, and applied to prototype structures based on the III-V /As and As/InP heterostructure systems. Single quantum wells are considered first. Transition energies are calculated and conveniently plotted as functions of composition (or strain) and layer thickness for both systems, and valence-subband band structures and k-dependent optical matrix elements are examined in detail for both systems in regimes where crossing of the uppermost light- and heavy-hole bands is induced by composition or well-width changes. Superlattices in both material systems are then considered, with emphasis on structures in which crossing of the uppermost valence subbands is induced by variation of barrier width. Band structures and optical matrix elements are calculated for wave vectors along directions parallel and perpendicular to the layer planes both in free-standing /As SL’s with strain shared between the well and barrier layers and As/InP SL’s strained to lattice match to InP substrates. Finally, general features of band structures and optical matrix elements in tensile-strained structures inferred from these studies are summarized. Implications for tensile-strained quantum-well lasers are discussed briefly.
- Received 20 December 1993
DOI:https://doi.org/10.1103/PhysRevB.49.10402
©1994 American Physical Society