  Secondary Ions Mass Spectroscopy and Hall effect measurements were performed
on boron doped silicon with concentration between 0.02 at.% and 12 at.%.
Ultra-high boron doping was made by saturating the chemisorption sites of a Si
wafer with BCl3, followed by nanosecond laser anneal (Gas Immersion Laser
Doping). The boron concentration varies thus nearly linearly with the number of
process repetitions. However, it is not the case for the hole concentration
which tends to saturate at high boron concentration. The difference between
boron and hole concentration increases as the square of boron concentration,
pointing towards the formation of boron pairs as the dominant contribution to
the increase of inactive boron.
