Evolution of photoluminescent defect clusters in proton- and copper-implanted silicon crystals during annealing

Evolution of intrinsic defects (interstitials or vacancies) formed by implanting with protons and copper ions in silicon crystals and then annealing the crystals at temperatures from 100 to 800 deg. C was investigated by photoluminescence (PL) measurements. For samples annealed below 400 deg. C, only the well known W and I3 center peaks were observed for both proton and copper implantations. Several no-phonon PL peaks (at least six), that were inferred to be due to interstitial clusters, were newly evolved between 1.2 to 1.4 μm for samples heavily implanted with both protons and copper ions after annealing between 500 and 600 deg. C, indicating the existence of several self-interstitial clusters having a stability between that of the W center and the {311} defects. From the dependences of the PL intensities of these new peaks on the densities of the displaced atoms formed by implantations and on the annealing temperatures, these clusters were thought to be composed of larger numbers of self-interstitials than the W center. In addition to these peaks (the W, I3, and new centers), several broad peaks seemingly due to plural origins were observed after annealing the heavily implanted samples from room temperature to 600 deg. C, however, they completely vanished after annealing at 700 deg. C. Evolution of the PL peak located at 1.376 μm and known to be due to the {311} defects was not observed after the annihilation of the preceding peaks that are presumed to be the precursors of the {311} peak