THEORY OF CARBON COMPLEXES IN ALUMINUM ARSENIDE

The structural and dynamic properties of carbon defects in aluminum ar senide are investigated using first-principles local-density-functiona l cluster theory. The method accounts satisfactorily for the structure and phonon modes of AlAs. The carbon acceptor and donor possess tripl et modes in the band gap between the acoustic and optic branches as we ll as localized triplet modes. The local mode of the acceptor lies wit hin 40 cm-1 of the observed mode. Four modes of a close-by acceptor pa ir lie within 40 cm-1 of the local mode of the isolated acceptor and t his supports a previous assignment of four satellite lines seen in hea vily doped material to this defect. The modes of a donor-acceptor pair are investigated but there is no evidence of their existence.