A sequence of three B-spikes in molecular-beam epitaxial material was studied. Secondary-ion mass spectrometry was used to investigate the mechanisms of B diffusion during irradiation with 2.5MeV protons at a sample temperature of 570C. The energy of the proton beam was chosen so that the generation rate of point defects could be considered to be uniform throughout the B δ-doped Si. The effect of the B concentration (ranging from 5 x 1015 to 3 x 1018/cm3) upon enhanced B diffusion was studied in detail. For each concentration, the B diffusion coefficient was increased by a factor of more than 5 x 104 under irradiation, as compared with the B diffusion coefficient at 570C in non-irradiated areas. To a first approximation, this enhancement was independent of the depth position of the B spike but depended upon the B concentration. The diffusion of B under irradiation exhibited an exponential behavior. This type of diffusion had already been reported for B diffusion in Si during oxidation at 600C.

Influence of Boron Concentration on the Enhanced Diffusion Observed after Irradiation of Boron Delta-Doped Silicon at 570C. P.Lévêque, J.S.Christensen, A.Y.Kuznetsov, B.G.Svensson, A.Nylandsted Larsen: Nuclear Instruments and Methods in Physics B, 2001, 178[1-4], 337-41