Reflectivity and transmittance investigations of photoexcited charge carriers in silicon in the picosecond time domain

Using picosecond laser pulses of a NdYAG laser system we studied relaxation processes in high-excited monocrystalline silicon by transient reflectivity and transmittance. An experimental setup will be presented which is very sensitive to small refractive index changes. By different excitation radiations, i.e. different induced carrier distributions it is possible to separate the influence of different relaxation processes as surface and bulk recombination and diffusion on the simultaneously measured transient reflectivity and transmittance. The parameters of these relaxation processes were found by fitting the experimental results with computer calculations.