Thermal stability and vibrational spectroscopy of N-O shallow donor centers in silicon

N-O-related shallow donors in nitrogen-doped Czochralski silicon have been studied by infrared spectroscopy. Quasithermal equilibrium states were established by long-term thermal annealing in the temperature range from 600 to 1000 degrees C. By quantitative analysis of the 1s -> 2p(+/-) far-infrared electronic transitions between 230 and 250 cm(-1), it is found that the formation and decay characteristics of these centers do not correspond to theoretical predictions. All complexes investigated show a monotonic decrease for annealing temperatures above 600 degrees C. In particular, the dominant NO2 complex exhibits a pronounced biexponential decay behavior. Based on the characteristic thermal fingerprint of the individual shallow donor species, associated local vibrational modes in the midinfrared were investigated. Two bands at 1070 and 860 cm(-1) can be assigned to NO2, the center with the highest concentration variation in the relevant temperature range between 600 and 800 degrees C. These frequencies match favorably with recent calculations for this complex in the symmetrical O-N-O configuration. (C) 2009 American Institute of Physics. [doi:10.1063/1.3253759]