Carbon oxygen and intrinsic defect interactions in germanium-doped silicon

摘要

Production and annealing of oxygen-vacancy (VO) and oxygen-carbon (C_iO_i,C_iO_i,I) defects in germanium-doped Czochralski-grown silicon (Cz-Si) containing carbon are investigated. All the samples were irradiated with 2 MeV fast electrons. Radiation-produced defects are studied using infrared spectroscopy by monitoring the relevant bands in optical spectra. For the VO defects, it is established that the doping with Ge affects the thermal stability of VO (830 cm~(-1)) defects as well as their fraction converted to VO_2 (888 cm~(-1)) defects. In Ge-free samples containing carbon, it was found that carbon impurity atoms do not affect the thermal stability of VO defects, although they affect the fraction of VO defects that is converted to VO2 complexes. Considering the oxygen-carbon complexes, it is established that the annealing of the 862 cm~(-1) band associated with the C_iO_i defects is accompanied with the emergence of the 1048 cm~(-1) band, which has earlier been assigned to the C_sO_2i center. The evolution of the C_iO_iI bands is also traced. Ge doping does not seem to affect the thermal stability of the C_iO_i and C_iO_iI defects. Density functional theory (DFT) calculations provide insights into the stability of the defect clusters (VO, C_iO_i, C_iO_iI) at an atomic level. Both experimental and theoretical results are consistent with the viewpoint that Ge affects the stability of the VO but does not influence the stability of the oxygen-carbon clusters. DFT calculations demonstrate that C attracts both O_i and VO pairs predominately forming next nearest neighbor clusters in contrast to Ge where the interactions with O_i and VO are more energetically favorable at nearest neighbor configurations.