Evidence for small interstitial clusters as the origin of photoluminescence W band in ion-implanted silicon

We have investigated the origin of the photoluminescence (PL) W band in ion -implanted Si by studying the temperature evolution and depth profile of th e related defects. Evolution of the PL spectra induced by postimplant annea ling is correlated to a transition of small interstitial clusters to extend ed {311} defects in self-ion-implanted Si. Growth of W band intensity after step-by-step removal of the damaged layer rules out the involvement of vac ancy-related defects in the formation of the W center and establishes that migrated and clustered interstitials give rise to an intense W band. The an nealing behavior and the thermally activated growth of the W center suggest the involvement of small interstitial clusters, larger than di-interstitia l. In accordance with recent results based on simulational studies, we argu e that the W center consists of tri-interstitial clusters of silicon. (C) 2 001 American Institute of Physics.