Anomalous excitation-power dependence of band-edge emission in Si involving radiation-induced defects

We report on the anomalous excitation-power dependence of the band-edge emission in Si after 2 MeV electron irradiation. It is well-established that the dependence of the emission intensity I on the excitation power L is generally follows the power law, I ∝ Lⁿ with the exponent n between 1 and 2. However, the exponent n increases after the electron irradiation and becomes larger than 2 at temperatures from 60 to 150 K in all the measured samples. The present dependence can be explained by a simple model: the radiation-induced defects act as dominant recombination centers in the low excitation-power range, but their activity becomes saturated in the high excitation-power range. (author)