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

Abstract

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 0.4to2.4THz. The key parameters determined from THz data using the Drude model are: the plasma frequency ωp=2.6±0.2THz, the average momentum relaxation time ⟨τ⟩=56±2fs, and the mobility μ=89cm2∕Vs for electrons. The THz absorption spectrum showed resonance structures attributed to the difference frequency combinations associated with acoustical and optical phonons.

Acceptor levels in GaSe:In crystals investigated by deep-level transient spectroscopy and photoluminescence

“…2- 4 The electrical and optical properties of GaSe doped with different elements could differ significantly compared to the properties of unintentionally doped GaSe. The identification of the donor and acceptor levels between the valence and conduction bands of GaSe is important in view of its further applications in photoelectronic devices, such as room temperature radiation detectors.…”

GaSe1−xSx and GaSe1−xTex thick crystals for broadband terahertz pulses generation

“…In GaSe, THz absorption is governed by free carrier absorption, second-order phonons, and localized impurity vibration modes. 16,17 Improving the growth technology should decrease absorption related to impurities. We note that the absorption peak at 0.59 THz that affects the spectra of THz generation for the thick GaSe crystals can be canceled out by adding only 2 mass % of Te.…”

Terahertz sources

“…TDTS and pump/probe setups based on OR sources are widely used to investigate the molecular spectra of a number of materials, including water, semiconductors, chemical, vapors, proteins, and bacteria. 11,16,[18][19][20][21][22][23][24][25][26] …”

“…The CCNY/IUSL has been engaged in 23 Freon-11 (CCl 3 F, CFC-11), 24 Bacillus subtilis spores and DPA, 25 semiconductor crystals GaSe, 26 and GaAs. 27 The THz-absorption spectra, refractive indices, dielectric properties, and phonon relaxation times were measured by the TDTS pump-probe method (see setup shown in Figs.…”