Terahertz studies of the dielectric response and second-order phonons in a GaSe crystal

The dielectric function and momentum relaxation time of carriers for a single-crystal GaSe were investigated using terahertz time-domain spectroscopy over the frequency range from 0.4 to 2.4 THz. The key parameters determined from THz data using the Drude model are: the plasma frequency omega(p)=2.6 +/- 0.2 THz, the average momentum relaxation time <tau >=56 +/- 2 fs, and the mobility mu=89 cm(2)/V s for electrons. The THz absorption spectrum showed resonance structures attributed to the difference frequency combinations associated with acoustical and optical phonons. (C) 2005 American Institute of Physics.