Aspects of point defects in coherent terahertz-wave spectroscopy

• DOI: 10.1016/j.physb.2007.09.050
• Publication Date: 2007-09-12T07:21:58Z
• Authors: Jun-ichi Nishizawa; Tetsuo Sasaki; Yutaka Oyama; Tadao Tanabe
• Keywords: 0103 physical sciences; 01 natural sciences

Abstract The e-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.