DYNAMICS OF THE H-C(AS) COMPLEX IN GAAS

Infrared-absorption measurements have been made on epitaxial layers of GaAs grown by metal-organic molecular-beam epitaxy and doped with either C-12 or C-13 impurities to a concentration of 1. 5 X 10(19) cm-3. After the introduction of either hydrogen or deuterium atoms from a radio-frequency plasma the localized vibrational modes (LVM) of H-C(As) pairs have been observed and analyzed. Two A1 modes and two E modes have been found for D-C(As) pairs, and so this is the first hydrogen-passivated shallow-impurity pair for which all four LVM's are present. Admixing of the two E modes explains an apparent anomaly when the spectra of samples containing H-C-12As are compared with those containing D-C-12As pairs. There is good agreement with published ab initio theory, and anharmonicity of the stretch modes is discussed. No evidence has been found for the presence of the other carbon complexes, nor for the amphoteric behavior of carbon.