Interference fringes in plane-wave topography of AlxGa1−xAs epitaxial layers implanted with Se ions

Abstract

The MOCVD grown Al 0.45 Ga 0.55 As epitaxial layers with low dislocation density, implanted with 1.5 MeV Se + ions to the doses 6×10 13 -4×10 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 μm was used to obtain a good resolution of interference maxima and to study the changes of the rocking curves in different regions of the sample. Due to the curvature of the samples, the interference maxima were revealed in plane wave topographs as interference fringes and the high intensity of the source enabled 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 boundary of implanted region was observed for the high angle side of the maximum due to epitaxial layer. A good approximation of experimental rocking curves and fringe pattern in the plane-wave topographs was obtained by numerical integration of the Takagi-Taupin equations assuming a strain profile with almost constant lattice parameter in a relatively thick layer close to the surface.