Lattice location and thermal evolution of small B complexes in crystalline Si

The lattice location of B in Si has been investigated by channelling analyses using nuclear reactions (650 keV proton beam, B-11(p,alpha)Be-8). The formation at room temperature of a specific, small B complex in presence of an excess of point defects has been inferred. In particular, B implanted in Si or B substitutional dissolved in Si and irradiated with proton beam form a unique B complex with B atoms not randomly located. The angular scans along the < 100 > and < 110 > axes are compatible with B-B pairs aligned along the < 100 > axis. The thermal annealing in the 200-950 degrees C range of the B complexes, analyzed by lattice location and carrier concentration measurements, depends on the residual defect density in the lattice. The B complexes dissolve at low temperature if no excess of Si self-interstitials (Is) exists or they evolve into large B clusters and then dissolve at high temperature if Is supersaturation holds.