Ultrafast dynamics at a silicon surface detected with femtosecond transient reflecting grating spectroscopy

The recently developed spectroscopic transient reflecting grating technique with a time resolution of 200 fs was applied to a silicon surface under the pump intensity of more than 1 mJ/cm(2). This method provides information on excited free carrier dynamics and subsequent heat generation and diffusion selectively based on appropriate choice of probe wavelength. With regard to the thermal component, the temperature at the surface increased within several picoseconds and then decayed after about 300 ps. As the pump intensity was increased, the maximum temperature rise showed a nonlinear dependence on it, and also the temperature rise time became faster. The results led to the conclusion that the carrier dynamics causing a temperature rise at a silicon surface is dominated mainly by Auger recombination, not by the decay to a band edge under the high carrier density conditions. (C) 2002 American Institute of Physics.