Femtosecond-timescale buildup of electron mobility in GaAs observed via ultrabroadband transient terahertz spectroscopy

摘要

The buildup of photoconductivity in an archetypal polar semiconductor GaAs was monitored on the timescale of carrier-carrier and carrier-lattice correlations, with sub-50 fs temporal resolution provided by ultra-broadband transient terahertz spectroscopy. Two relevant timescales are identified: the transition in photoconductivity from a regime of extremely weak screening to a screened Drude plasma was observed on the ~280 fs timescale, followed by the gradual increase and saturation of electron mobility on a timescale of ~ 160 fs. The Drude photoconductivity picture following carrier photoinjection was found to stabilize only on the timescale corresponding to several lattice and plasma oscillations.