Self-interstitial migration during ion irradiation of boron delta-doped silicon

Boron delta layers in silicon, grown by molecular beam epitaxy and characte rized by the secondary ion mass spectrometry, have been employed to investi gate the migration of silicon self-interstitials during irradiation with Me V protons in the 500-850 degreesC temperature range. After growth, the samp les were thinned from the backside to a thickness that made them transparen t for the proton energies used. As a result, the generation rate of point d efects can be considered as essentially uniform throughout the samples. How ever: the evolution of the boron profiles is almost identical to that obser ved after injection of self-interstitials caused by thermal oxidation of th e samples at elevated temperature. This strongly indicates that the surface acts as a reflective boundary for the migrating self-interstitials or/ and an efficient sink for mobile vacancies. Furthermore, higher value of inter stitial supersaturation in the near-surface region in proton-irradiated sam ples is consistent with experimentally detected depth dependence for immobi le fraction in boron clusters. Then, activation energy of boron mobilizatio n, (0.9 +/- 0.4) eV, was attributed to the dissociation of boron clusters. (C) 2000 Elsevier Science Ltd. All rights reserved.