Local vibrational modes in GaAs under hydrostatic pressure

Abstract

Using infrared spectroscopy, we have observed local vibrational modes (LVM's) in GaAs at hydrostatic pressures as high as 7 GPa at liquid-helium temperatures. The shift of the infrared-active ${v}_{3}$vibrational mode of ${\mathrm{CO}}_{2}$ impurities in the ${\mathrm{N}}_{2}$ pressure medium was used as an in situ pressure calibration. We find that LVM's arising from ${}^{12}{\mathrm{C}}_{\mathrm{As}}$ and ${}^{13}{\mathrm{C}}_{\mathrm{As}}$ substitutional impurities vary linearly with pressure. The shifts of the ${}^{12}{\mathrm{C}}_{\mathrm{As}}\ensuremath{-}\mathrm{H}$ and ${}^{13}{\mathrm{C}}_{\mathrm{As}}\ensuremath{-}\mathrm{H}$ stretch modes have positive curvatures, while the pressure-dependent shift of the S-H stretch mode has a negative curvature.