Aspects of point defects in coherent terahertz-wave spectroscopy

Jun ichi Nishizawa, Tetsuo Sasaki, Yutaka Oyama, Tadao Tanabe

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


The ε-type monocrystalline GaSe crystals were successfully grown by liquid phase epitaxy at constant and low (530-590 °C) growth temperatures under different Se vapor pressures (PSe∼0-7.75 Torr). From coherent terahertz (THz)-wave spectroscopy, the absorption spectra have different resonant frequencies and absorption coefficients due to the stoichiometry-dependent point defects, which depend on the applied PSe. It is shown that the resonance in GaSe under PSe∼0 Torr shifts toward lower THz frequencies compared with those under high PSe, maybe due to the degraded intermolecular interactions caused by the introduction of selenium vacancy-related defects. The absorption coefficients (1-5 THz) decreased according to the increase of Se vapor pressure, thus the transparency of GaSe under higher PSe is improved by 25% compared with that of Bridgeman-grown crystals. It is revolutional method, in which value of Q could be as high as 3 million, for the molecular structure and defects in organic molecule also could be already analyzed.

Original languageEnglish
Pages (from-to)677-681
Number of pages5
JournalPhysica B: Condensed Matter
Publication statusPublished - 2007 Dec 15
Externally publishedYes


  • Coherent THz spectroscopy
  • GaSe
  • Point defects
  • Stoichiometry

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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