Progress in the growth and research of crystals for wide-gap semiconducting materials

The feasibility of a sublimation sandwich method for controlled growth of s ingle crystals and epitaxial layers of different SiC and GaN polytypes is d emonstrated. The controlled production of pure (n(i) < 10(16) cm(-3)) and h eavily-doped crystals and epitaxial layers of these materials has made it p ossible to study their semiconducting parameters in detail and to identify the nature of a number of the most important impurity centers. It is shown for the example of SiC that the typically high chemical-binding energy of a toms in these compounds is the reason for the formation of stable metastabl e compounds, among them associations and clusters that include intrinsic de fects which have a significant effect on the properties of the material. Cl usters formed on the surface can serve as seeds for different polytypes dur ing crystal growth. (C) 1999 American Institute of Physics. [S1063-7834(99) 01605-6].