The behavior of defects which had been introduced into heavily C-doped material, by high-temperature annealing, was studied. It was found that C-related defects decreased hole concentration and mobility, C concentration on the As sub-lattice, and recombination lifetime. It was proposed that extrinsic or intrinsic Frenkel-type defect formation would occur on the sub-lattices, thus resulting in the formation of As vacancies as well as C interstitials. It was experimentally deduced that one defect formation reaction consumed 3 holes, although the theoretical prediction was 4 holes. The driving force for such reactions was expected to be the equilibration of As vacancies at high temperatures. It was suggested that the origin of scattering centers was not the same as that of recombination centers. From a comparison of the capture cross-sections of recombination centers and scattering centers, it was deduced that a secondary reaction should follow and generate recombination centers. That is, C interstitials might combine with C acceptors so as to form di-carbon interstitials, and As vacancies might combine with C acceptors to from complexes. It was pointed out that interstitial C, or As vacancies, played an important role in the degradation of devices with heavily C-doped layers.

H.Fushimi, K.Wada: Journal of Applied Physics, 1997, 82[3], 1208-13