Vapour pressure controlled Czochralski monocrystals of semi-insulating GaAs were investigated, for the first time, by means of synchrotron X-ray topography. The X-ray topographs of a typical sample, taken from the cylindrical part, revealed dislocation images which resembled those from semi-insulating vertical gradient freeze-grown GaAs crystals. From the disappearance of the dislocation image in selected topographs it was concluded that the Burgers vector for most dislocations was parallel to <110>. The majority proved to be of 60° type. The cellular structure, which was typical of liquid encapsulated Czochralski material, was not seen in these samples. Large volumes (up to 0.5mm x 0.5mm x 0.5mm) were dislocation-free. The results were compared with etch-pit density measurements of the same crystals. The average etch-pit density was 104 to 2 x 104/cm2. The minimum value along <110> was 2 x 103/cm2.

Synchrotron X-Ray Topography of Undoped VCz GaAs Crystals. T.Tuomi, L.Knuuttila, J.Riikonen, P.J.McNally, W.M.Chen, J.Kanatharana, M.Neubert, P.Rudolph: Journal of Crystal Growth, 2002, 237-239, 350-5