Calculations of the electronic structure of highly strained GaAs/GaSb/GaAs heterostructures

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Abstract
The band offsets at the highly strained GaAs/GaSb (7% lattice mismatch, with the GaAs unstrained) and the lattice-matched GaAs/AlAs [001]-oriented interfaces have been determined with use of self-consistent pseudopotential techniques. The linear and quadratic deformation potentials of GaSb under biaxial strain have also been calculated. The valence-band offset at the ideal GaAs/GaSb interface is predicted to be 1.10 eV, with the strained GaSb valence band being higher in energy, in good agreement with the model-solid theory. The confinement energies of the first heavy- and light-hole states are determined with use of the effective-mass approximation. The lowest direct optical transition is at 0.64 eV, which is considerably smaller than the value of about 1.30 eV obtained in recent experiments. This discrepancy is discussed in some detail, and it is most probably due to incorporation of As atoms in the GaSb region in the experimental samples.