Determination of Carrier-Carrier and Carrier-Phonon Relaxation Time from Ultrafast Photoinduced Absorption in Amorphous Semiconductors.

摘要

Femtosecond laser spectroscopy has been used to study carrier relaxation times in amorphous silicon. We find a relaxation time of 1 picosecond above the mobility edge and a relaxation time of 10 picoseconds in the bandtail states, after which temperature effects dominate the optical properties. Theoretical modeling of femtosecond spectroscopic measurements has also helped define what is measurable and what is not. Picosecond time-resolved reflectivity measurements have been performed during laser-induced phase transitions. The dielectric function of molten Si hs been measured and superheating in the liquid phase has been observed at least to 10 picoseconds. Keywords: Free electron laser; Time resolved (picosecond and femtosecond); Spectroscopy; Amorphous semiconductors; Laser-induced phase transitions. Reprints. (JHD)