Effective energy gap of semiconductors under irradiation with an ultrashort VUV laser pulseN. Medvedev and B. Rethfeld
Technical University of Kaiserslautern and OPTIMAS Research Center - Erwin Schroedinger Str. 46, D-67663 Kaiserslautern, Germany, EU
received 26 October 2009; accepted in final form 12 November 2009; published December 2009
published online 27 November 2009
We study theoretically the electronic excitation within semiconductors under irradiation with an ultrashort VUV laser pulse as provided by the new free-electron laser FLASH in Hamburg, Germany. Applying Monte Carlo technique we obtain the transient distribution of the excited electrons within solid silicon. We find the statistical nature of an effective energy gap for multiple electronic excitation, providing the fundamental understanding of the experimentally accessible pair creation energy measured as a long time limit. Considering photoabsorbtion, impact ionizations and Coster-Kroning transitions, we estimate the pair creation energy and give a general formula to calculate the effective energy gap for semiconductors.
52.50.Jm - Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.).
61.82.Fk - Radiation effects on specific materials: Semiconductors.
06.60.Jn - High-speed techniques (microsecond to femtosecond).
© EPLA 2009