Infrared absorption peaks in nitrogen doped CZ silicon

Dependences on annealing temperature and nitrogen concentration were examined for new local vibration mode infrared absorption peaks at 856, 973, 984 and 1002 cm−1 in nitrogen-doped CZ silicon crystal. The new absorption peaks were so weak that two sets of samples were examined for temperature and concentration dependences, respectively, to get reliable results. The peak at 1002 cm−1 behaved similarly for annealing, though much weaker, to the known peaks at 810 and 1018 cm−1 which are attributed to interstitial N pair accompanied by the two oxygen interstitials (NNOiOi). This suggests that the origin contains 2 Oi also. It was strong in low concentration regime, which is similar to the behavior of shallow thermal donors. This suggests that the structure contains one nitrogen rather than two (N–O interstitial pair). The results were compared with the electronic transition absorption by shallow thermal donors (STD). The absorptions at 1002 and 240 cm−1 behaved similarly. These suggest that the peak at 1002 cm−1 is likely due to NOOiOi which is the candidate for STD. The temperature dependence of the other new peaks was slightly different from each other. Origin of the other peaks is not clear yet.