Overcoordinated hydrogens in the carbon vacancy : Donor centers of SiC

• Epitaxial silicon carbide is likely to contain hydrogen and vacancies (V), therefore, V + nH complexes are likely to influence its electronic properties. Using ob initio calculations we show that neutral and positive H atoms are trapped by carbon vacancies (V-C) in three-center bonds with two Si neighbors. The double positive charge state of V-C + H is not stable in equilibrium and in the triply positive state H binds only to one of the Si neighbors. At most two H atoms can be accommodated by a single V-C. The V-C + nH complexes have donor character and exhibit rather atypical vibration modes for Si-H bonds. Occupation levels and spin distributions were calculated and compared fur V-C + H and V-C.

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