B implanted at room temperature in crystalline Si: B defect formation and dissolution

The B lattice location of B implanted into crystalline Si at room temperature has been investigated using the nuclear reaction B-11(p,alpha)(8)be induced by 650 keV proton beam and channelling analyses. The angular scans along the (100) and (110) axes indicate the formation of a particular B complex with B atoms non-randomly located. The same defect has been observed also for B doped Si where the B atoms, initially substitutional and electrically active, have been displaced as consequence of the interaction with the point defects generated by proton irradiation. The angular scans were compatible with the B-B pairs aligned along the (100) axis predicted by theoretical calculations. The thermal evolution in the 400-950 degrees C range of the B complexes has been inferred both by B lattice location measurements and electrical activation. At low temperature (< 700 degrees C) only 10% of the total B dose is active and a significant increase of randomly located B occurs. A significant electrical activation consistent with the concentration of substitutional B occurs at temperature higher than 800 degrees C. The data are interpreted in terms of a formation and dissolution of the B complexes