OH bonds in gallium arsenide grown by the liquid-encapsulated Czochralski crystal-growth method

H-related vibrational lines observed at 6 K between 2940 and 3500 ${\mathrm{cm}}^{\mathrm{-}1}$ in O-containing semi-insulating GaAs samples are attributed to OH and NH modes. The detection of an ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ mode enables us to assign the strongest line of the spectrum to an OH mode in a semiconductor. In samples where holes can be emitted during photoneutralization of EL2 defects, the intensity of many of these lines is photosensitive and additional vibrational lines appear after near-infrared illumination. This photosensitivity is not due to a metastability effect, but rather to different charge states of the centers where these OH and NH bonds are included and it is interpreted as the capture of a hole by the center. Stress-induced splitting of some lines could be studied in one sample; and for one line, the splitting was interpreted by assuming two simultaneously possible orientations of an OH bond and a low-temperature reorientation of this bond under stress. Tentative models are given for the centers associated with two of these lines.