Strain effects on the microscopic structure of an InGaAs epilayer in InGaAs/GaAs heterostructures: a theoretical study

Several strained structures of two ideal In Gaz 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 Bne-structure results on strained In Gaz As/GaAs heterostructures. The achieved results show that the strain is accomodated by signi6cant 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 accomodation occurring in the In Ga& As epilayer. Anisotropic strain eKects are found, which lead to two diferent next-nearest-neighbor distances for atomic pairs on and out of the planes parallel to the In Gaq As/GaAs interfaces.