Abstract
A sensitive pump and probe method for measuring the transient carrier density in semiconductors is proposed and demonstrated in silicon. It relies on the magnified reflectivity changes when the picosecond probe laser is incident close to Brewster’s angle. We have measured the Auger recombination coefficient γ=2×10−31 cm6 s−1 and, in microcrystalline silicon films on insulator, the effective lifetime due to grain boundaries τ≂100 ps. Additionally, at much higher pump energies, upon melting, the reflectivity jumps by nearly one order of magnitude.