Annealing studies of point defects in low dose MeV ion implanted silicon

Abstract

Deep Level Transient Spectroscopy studies of Czochralski grown n-type (phosphorous doped) silicon, implanted with low doses of 5.6 MeV Si ions at room temperature and later annealed are presented. A prominent acceptor type defect is observed in all annealed samples which is located at 0.32 eV below the conduction band edge, E c and has a capture cross section of ∼ 10 −15 cm 2. We attribute this defect to be a hydrogen related complex, presumably, a defect formed with the interaction of divacancy centres and dissolved hydrogen present in the as-grown silicon. Thermal stability of irradiation induced point defects has also been studied. It is observed that the divacancy (V 2) and vacancy oxygen (VO) centres produced after ion implantation disappear at lower temperatures compared to electron irradiated, high purity float zone (FZ) samples. This is mainly attributed to the fact that MeV ion implantation results in the formation of a non-uniform defect distribution and hence enhances diffusion of point defects until they are annihilated through reactions with traps in the implanted material e.g., interstitial oxygen atoms, substitutional carbon atoms, hydrogen atoms and/or localised disordered regions.