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Di-carbon complexes in AlAs and GaAs

Di-Kohlenstoff-Komplexe in AlAs und GaAs


Physica status solidi. B 210 (1998), pp.869-872 : Ill., Lit.
ISSN: 0031-8957
ISSN: 0370-1972
Journal Article
Fraunhofer IAF ()
AlAs; carbon doping; GaAs; Kohlenstoffdotierung

Heat treatment of heavily carbon doped AlAs and GaAs results in a loss of C(As) shallow acceptors. In Raman scattering experiments on annealed CBE grown GaAs with 12.C and 13.C isotopes, and MOVPE grown AlAs it is found that the loss of carriers is accompanied by the appearance of two high frequency lines. These lie near to the stretch mode of an isolated C2 molecule (1855 cm (-1)). This is consistent with the formation of two types of di-carbon defects in these materials where the C atoms are bonded together and one or both of which act as a donor. Using a local density functional method to investigate the structure and dynamics of several di-carbon defects, we find that the dimer at an As site is bistable and aligned approximately in a (100) direction in the neutral charge state, and in a (110) direction when positively ionised. The calculated frequencies lie within 10 per cent of the measured values in both materials. Other defects are investigated too with a view of determining the structures giving rise to the modes.