The H passivation of C acceptors, and the stability of defect complexes which contained C and H, were studied by means of first-principles pseudopotential calculations. A C-H complex, CAs--(HCAs)0, with two CAs atoms located at second-nearest neighbor As sites was found to be energetically more favorable than an isolated configuration of CAs- and H-CAs. It was also found that a (H-CAs)2 complex which contained two H atoms was more stable than were 2 isolated H-CAs pairs. Moreover, H dissociation from the CAs--(HCAs)0 center during annealing led to the formation of a CAs-CAs pair. The latter complex then dissociated into 2 isolated CAs acceptors. A dissociation process was proposed here which involved a C-C split-interstitial complex at an As site, plus a second-nearest neighbor As vacancy. The associated energy barrier (about 1.7eV) was similar to that for Zn diffusion.

Atomic Structure of Defect Complexes Containing Carbon and Hydrogen in GaAs. S.G.Lee, K.J.Chang: Physical Review B, 1996, 54[12], 8522-6