Growth-twinning in zincblende crystals: further insights from studies of liquid encapsulated Czochralski (LEC) grown InP single crystals

Synchrotron white beam X-ray topography (SWBXT) combined with chemical etching and Nomarski optical microscopy have been employed to investigate the phenomenon of twinning in sulfur doped, LEC grown ⟨100⟩ InP single crystals. Results confirm the general prediction of Hurle that twins nucleate in regions where {111} edge facets are anchored to the three phase boundary (TPB), and that twinning produces a {111} external facet on the shoulder region of the crystal. However, some specific aspects of Hurle´s theory were corrected by this experimental study. A detailed X-ray examination revealed the appearance of a {115} external shoulder facet immediately before the occurrence of twinning. The location at which the twin nucleates is the point where the {115} shoulder facet is converted to a {111} external shoulder facet. This twinning mechanism allows for a reduction in free energy by converting the facet from a {115} to a {111} plane