SYNCHROTRON WHITE-BEAM TOPOGRAPHIC STUDIES OF GALLIUM-ARSENIDE CRYSTALS

A series of samples cut out from different types of gallium arsenide c rystals with low dislocation density were studied by means of white be am synchrotron topography. The investigation was performed with transm ission and back-reflection projection methods and transmission section method. Some of tile topographs in transmission geometry provided a v ery high sensitivity suitable for revealing small precipitates. The tr ansmission section images significantly differed depending on the wave length and absorption. In some cases a distinct Pendellosung fringes a nd fine details of dislocation and precipitates images were observed. It was possible to reproduce the character of these images by means of numerical simulation based on integration of TakaKi-Taupin equations. Due to more convenient choice of radiation, synchrotron back-reflecti on projection topography provided much better visibility of dislocatio ns than analogous methods realized with conventional X-ray sources.