Synchrotron-radiation plane-wave topography I. Application to misfit dislocation imaging in III-V heterojunctions

The extremely parallel and monochromatic beam (divergence ∼ 0·3″, spectral width Δλ/λ ∼ 7 × 10−6) extracted from the white synchrotron-radiation X-ray beam by a multiple reflection single-crystal monochromator has been used to record plane-wave reflection topographs. Separate images of a quaternary epilayer, Ga0.7Al0.3As1-yPy and a GaAs substrate building up a nearly matched heterostructure have been obtained. Typical thin-crystal features are observed in the epilayer. Differences in the interface dislocation contrast and strain field are revealed between the layer and substrate. By increasing the local departure from Bragg incidence (weak-beam condition), images as narrow as 1 μm can be obtained.