Abstract

ABSTRACT Kinetics of the decay of a dynamical grating formed by nonequilibrium charge carriers in thin monocrystalline siliconfilms under femtosecond laser excitation are studied. A case of limiting concentration of charge carriers (Nl 21 cm3) is analyzed. Contributions of ambipolar diffusion and Auger-recombination in the decay of a dynamical grating areestimated. At high intensities (>5 10 W/cm2) an effect ofthe long-lived (12 ps) dynamical grating is discovered.Keywords: semiconductor, dynamics of free charge carriers, femtosecond excitation. 1. INTRODUCTION At present dynamics of free charge carriers in semiconductors produced by pico- and femtosecond laser pulses are ofgreat interest. This interest is due to the formation of strongly nonequilibrium states of electron and phonon subsystemsin a semiconductor. Under femtosecond laser pulses with a peak intensity of I1O12 W/cm2 highly overheated electron-hole plasma with a charge concentration of N 1 02 1 cm3 may be generated [1 -3]. Decay of these nonequilibrium statesoccurs during the time t=1O12-lO'4 s and is due to the influence of several competing mechanisms [1-7]. The aim ofthis paper is to estimate the extent of the influence of the main mechanisms of the decay of electron—hole plasma inmonocrystalline Si films on the process on the whole.

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