Voids in silicon substrates for novel applications

The mechanisms of He-bubble and, after annealing, of void formation is described. Size effects of protrusions of the implanted region indicate a He diffusion mechanism and an interaction with vacancies and divacancies for the bubble formation. PL has revealed helium inside divacancies in the same range of temperatures where self-interstitials, produced during implantation, have been observed to recombine at the sample surface. As a consequence the inversion in the vacancy-interstitial balance is produced and a supersaturation of vacancies is observed. The main properties of voids when used to getter metal impurities or to control locally lifetime are also described and discussed.