X-ray-diffraction measurements from imperfect GaAs crystals: Evidence for near-surface defects

Gallium arsenide crystals with orientations [1{} 1{} 1{}] and [111] were measured with use of a three-crystal x-ray diffractometer. Owing to the preparation of the surface of the substrates and the growing conditions using molecular-beam epitaxy (MBE), a concentration of large defect clusters of several parts per million in the MBE-grown layers results. These defects cause considerable diffuse scattering, which is visible around the reciprocal-lattice points. Even for evaporated MBE layers with thicknesses of only about 3000 {}, diffusely scattered intensity can be detected.