Interference fringes in plane-wave topography of AlxCa1-xAs epitaxial layers implanted with Se ions

The MOCVD grown Al0.45Ga0.55As epitaxial layers with low dislocation densit y, implanted with 1.5 MeV Se+ ions to the doses 6X10(13)-4X10(14) ions/cm(2 ), were studied using a multicrystal arrangement and applying synchrotron X -ray radiation. A very small size of the probe beam close to 30 mu m was us ed to obtain a good resolution of interference maxima and to study the chan ges of the rocking curves in different regions of the sample. Due to the cu rvature of the samples, the interference maxima were revealed in plane wave topographs as interference fringes and the high intensity of the source en abled studying of the fringes also in these regions of the curve where the reflected intensity is very low. The continuity of the fringes across the b oundary of implanted region was observed for the high angle side of the max imum due to epitaxial layer. A good approximation of experimental rocking c urves and fringe pattern in the plane-wave topographs was obtained by numer ical integration of the Takagi-Taupin equations assuming a strain profile w ith almost constant lattice parameter in a relatively thick layer close to the surface. (C) 1999 Elsevier Science B.V. All rights reserved.