Strain effects on the microscopic structure of an InxGa1-xAs epilayer in InxGa1-xAs/GaAs heterostructures: A theoretical study.

Abstract

Several strained structures of two ideal ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As compounds have been investigated by performing ab initio total-energy and atomic-force calculations in order to give a microscopic interpretation of extended x-ray-absorption fine-structure results on strained ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs heterostructures. The achieved results show that the strain is accommodated by significant bond-angle distortions and small In-As bond contractions. A striking, stretched Ga-As distance (close to the In-As one) observed in the strained heterostructures should not be related therefore to the strain accommodation occurring in the ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As epilayer. Anisotropic strain effects are found, which lead to two different next-nearest-neighbor distances for atomic pairs on and out of the planes parallel to the ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs interfaces.