Optical properties of semiconductor GaSe1-xSx ( 0 ≦ x ≦ 1)

• Main Authors: Tz-Fang Huang, 黃姿方
• Other Authors: Hsiang-Lin Liu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/74825730219446336473

碩士 === 國立臺灣師範大學 === 物理學系 === 98 === We report the optical properties of GaSe1-xSx (x = 0, 0.01, 0.03, 0.14, 0.18, 0.26, 0.37, and 1.00) single crystals. Room-temperature Raman-scattering spectrum of GaSe exhibits four phonon peaks at about 134 cm-1, 212 cm-1, 250 cm-1, and 307 cm-1. With increasing sulfur concentration, these Raman lines shift toward higher frequencies. When x ≧ 0.18, additional phonon mode appears at about 160 cm-1 and this phonon gradually hardens to 188.5 cm-1 in GaS, reflecting GaSe1-xSx crystallizes in the different kinds of stacking phases as the sulfur doping increases. Moreover, the linewidth of photoluminescence spectra broadens significantly and its peak position becomes larger than the values of energy gap at x ≧ 0.18. These changes are due to the modification of electronic structures when doped with S on Se in GaSe1-xSx. Additionally, the room-temperature infrared and optical reflectance and transmittance spectra of GaSe show one phonon resonance at about 210 cm-1 and an electronic transition at about 1.98 eV. Notably, their peak positions shift toward higher frequencies with an increase of sulfur concentration. The temperature variation of the values of energy gap reveals different trends at x ≧ 0.18. All of these observables suggest that sulfur doping causes significant changes in the stack phases of GaSe1-xSx. Finally, the first-principles theoretical calculations were used to predict the frequencies of vibrational modes at the Γ point in GaSe, and compare with the experimental results.