High resolution measurement of the carbon localized vibrational mode in gallium arsenide

The localized vibrational mode of carbon substituted at arsenic sites in gallium arsenide (GaAs) was measured with infrared absorption spectroscopy at 0.005 $cm−1$ resolution. Well-resolved fine structures were observed, yielding quantitative information on the line half widths and intensities. The relative intensities of the isotope lines are well fitted to a probability factor calculation using a natural abundance of 55.3% $Ga69.$ One explanation considered is that the dipole moment due to the relative displacement of carbon with respect to the gallium atoms has a tendency to be larger when the neighboring gallium atoms are heavier $(71Ga).$