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The growth of single‐crystal epitaxial layers of onto (0001) oriented sapphire substrates from the liquid phase is shown to require three conditions:(i) the partial pressure of in the H2 ambient, greater than the equilibrium pressure, (ii) the growth melt positioned in a thermal gradient to transport the dissolved to the growth interface, and (iii) the control of nucleation by the addition of Bi to the growth melt. Studies of growth at temperatures from 850° to 1050°C show that the layer thickness, , is approximately linear in time and varies with growth temperature and atom fraction of Ga, in the growth melt. When , internal cracks in the basal plane hexagonal directions develop at the layer‐substrate interface and for they propagate to the surface and are thermally etched. A description is given of the interaction of liquid Ga with as a function of and . The low solubility of in Ga ( fraction at 1150°C) prevents useful growth by slow cooling of the melt. The inability to change the electron concentration, , with Zn doping and the decrease of with in the growth melt support but do not unambiguously confirm the model that the native donor is a nitrogen vacancy
Logan et al. (Sat,) studied this question.