Observation of nonequilibrium carrier distribution in Ge, Si, and GaAs by terahertz pump-terahertz probe measurements

By J. Hebling, Matthias Hoffmann, H. Hwang, K. Yeh, Keith A. Nelson. 2009

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We compare the observed strong saturation of the free-carrier absorption in $n$-type semiconductors at 300 K in the terahertz (THz) frequency range when single-cycle pulses with intensities up to $150\text{ }\text{MW}/{\text{cm}}^{2}$ are used. In the case of germanium, a small increase in the absorption occurs at intermediate THz pulse energies. The recovery of the free-carrier absorption was monitored by time-resolved THz pump\char21{}THz probe measurements. At short probe delay times, the frequency response of germanium cannot be fitted by the Drude model. We attribute these unique phenomena of Ge to dynamical overpopulation of the high mobility $\ensuremath{\Gamma}$ conduction-band valley.

Subfields: Atomic and Molecular Physics, and Optics, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/3f483bef918697b7395877995093aa44cf62e096