High Resolution X-ray Diffractometry and Topography of Float-Zone GaAs Crystals Grown in Microgravity

Abstract

Abstract High resolution Bragg-case X-ray double and triple axis diffractometry and Laue-case white beam synchrotron X-ray topography experiments have been performed on undoped [001] oriented float-zone GaAs crystals have been grown under microgravity conditions in space on the D2 mission. Near the seed, excellent anomalous transmission was achieved and a clear cellular structure of dislocations observed. The double and triple axis rocking curves were comparable with those from semi-insulating terrestrial material. Following a heater failure, the molten zone height dropped and reciprocal space maps revealed a long ridge of scatter transverse to the diffraction vector direction. This corresponds to the presence of a distribution of sub-grains containing little internal strain. Continued growth resulted in twin formation.