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Two vibrational absorption lines at 3015.5 and 3092.8 cm -1 , observed in liquid encapsulation Czochralski-grown GaAs, are investigated and are assigned to hydrogen stretching modes. The intensities of both lines measured in different samples are strictly correlated. Samples containing both hydrogen and deuterium show six additional lines, which are related to those. Two of them are located close to them and four lie in the region of the deuterium stretching modes. This result indicates that a di-hydrogen complex H A -X-H B is responsible for the lines, where the two hydrogen are bonded on inequivalent positions A and B to an atom X. The four values r = ω(H)/ω(D)1.34 of the stretching modes show that X must be a light impurity atom, probably oxygen. Illumination with light hv > 0.75 eV at T < 90K results in a decrease of the intensity of the eight lines and the simultaneous appearance of eight new lines. This effect is due to the capture of photogenerated holes by the H A -X-H B complex. |
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