Infrared spectrophotometry of carbon-induced localized vibrational mode in indium-doped liquid-encapsulated Czochralski GaAs

Infrared absorption measurements are performed for a carbon-induced localized vibrational mode in indium-doped semi-insulating GaAs crystals. Increase of the indium concentration in GaAs is found to result in a shift of the absorption peak to the lower energy side and a broadening of full width at half-maximum of the peak. The peak shift of 1 cm−1 corresponds to the change of indium concentration by 2.7×1020 cm−3. For a quantitative analysis of carbon, infrared absorptions are compared with carbon concentrations measured by secondary ion mass spectrometry. The absorption intensity of 1 cm−2 is found to correspond to the carbon concentration of (2.3±1.0)×1016 cm−3.