MBE GROWN GAAS ON GAAS (001) - UHV X-RAY-DIFFRACTION MEASUREMENTS

MBE grown gallium arsenide crystals with (001) orientation were investigated with a three-crystal x-ray diffractometer under UHV conditions. In the region of total external reflection (Q < 0.3 angstrom-1) no Kiessig fringes occur and hence no electron density difference between the substrate and the MBE layer exists. In the tails of the 004 Bragg reflection, modulations are observed. They are ascribed to a phase shift at the substrate-layer interface originating from a misfit parallel to the surface normal or a thin intermediate layer. The method can be applied to other thin film systems like oxidized or buried layers.