Abstract
We report the observation of hot carrier relaxation in silicon obtained by time-resolved reflectivity. The measurements were made under tow carrier density (~1017 cm−3) for which carrier-carrier processes are negligible and were facilitated by the greater than order of magnitude enhancement of the change in reflectivity signals that can be produced by the use of thin films. Carriers are injected into the 0.5-μm thick film of silicon with 70-fs optical pulses at 825 nm (2.0 eV) from a dispersion-compensated colliding-pulse-mode-locked (opm) dye laser. Initially, these carriers have substantial excess kinetic energy (~0.85 eV), since the band gap of silicon is only 1.15 eV at room temperature. Changes in reflectivity of a probe beam at the same wavelength are measured as a function of time with ~100-fs temporal resolution and sensitivity better than 1 part in 106 using an apparatus described previously.1 By monitoring the sample reflectance, we were able to follow the evolution of the carriers as they relax to the band edge.
© 1988 Optical Society of America
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