Isotopic study of mid-infrared vibrational modes in GaAs related to carbon and nitrogen impurities

Fourier transform infrared absorption measurements have been carried out on GaAs crystals doped or implanted with carbon, nitrogen and oxygen. In the presence of carbon and nitrogen, thermally stable defects occur with strong molecular-like bonding giving rise to absorption bands of vibrational character in the mid-infrared. By implantation of the nitrogen isotopes 14N and 15N, a complex of the chemical composition CN2 is identified. This defect is the origin for the mode at 2060 cm−1 previously attributed to a (C, O)-complex. A further absorption band at 1973 cm−1 is tentatively attributed to the stretching mode of a CN entity.