Local structure in semiconductor superlattices and epilayers

We report XAFS studies of two related strained semiconductor systems: nomin ally matched short period InGaAs/InP(001) superlattices and strained epilay ers of InxGa1-xAs on InP(001). In InGaAs/InP superlattices coordination num bers deviate significantly from the abrupt interface case, demonstrating th e presence of strained interface layers. This provides a local structural e xplanation for the non-negligible average lattice mismatch measured by diff raction. The analysis of strained epilayers of InxGa1-xAs/InP(001) allows u s to study in detail bond lengths in strained semiconductors. We demonstrat e that, notwithstanding the rigidity of semiconductor bonds, strain induces variations of nearest neighbor distances: bond lengths can be stretched or compressed. A model which reproduces strain-induced variations is presente d.