Determination of interfacial strain distribution in quantum-wire structures by synchrotron x-ray scattering

High-resolution grating x-ray diffraction from a periodic quantum-wire structure is shown to be highly sensitive to strain-field variations near a surface or an interface. Information on two types of strain gradients can be obtained: a longitudinal gradient, which can produce asymmetric diffraction profiles, and a transverse gradient, which can generate additional diffuse intensity streaks in reciprocal space. These effects are demonstrated in a synchrotron x-ray experiment on an ${\mathrm{In}}_{0.2}$ ${\mathrm{Ga}}_{0.8}$As/GaAs quantum-wire array. Kinematical diffraction theory is used to describe the diffraction patterns and is found to agree very well with the experimental results.