Ultrafast Carrier Relaxation in Hydrogenated Amorphous Silicon.

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 not. Picosecond-time resolved reflectivity measurements have been performed during laser induced phase transitions. The dielectric function of molten Si has been measured and superheating in the liquid phase has been observed at least to 10 picoseconds. Work continues in both areas. We expect to expand the experimental program to other wavelengths thanks to the free electron laser. Keywords: Free electron laser; Time-resolved (picosecond and femtosecond) spectroscopy; Amorphous semiconductors; Laser-induced phase transitions. Reprints. (AW)