Transmission study of picosecond photocarrier dynamics in free-standing porous silicon

Abstract Pump and probe technique has been used to study time-resolved differential absorbance of free-standing porous silicon at room temperature. The second (532 nm) harmonics of a mode-locked Nd 3+ :YAG picosecond laser served as pump pulses and the fundamental frequency (1.06 μm) were used as probe pulses. Photocarrier dynamics shows a fast decay in time domain of hundred picoseconds. A model of bimolecular radiative recombination is suggested, the values of bimolecular radiative recombination coefficient B and excited carrier cross section σ have been found to be B = 4 × 10 −10 cm 3 s −1 and σ = 9 × 10 −18 cm 2 , very close to the values reported for direct gap semiconductors.