Local hydrogen vibrational modes in GaAs doped with chalcogenides

Infrared absorption on GaAs doped with Chalcogenides under hydrogen plasma treatment has shown the presence of two new localised modes, namely stretch ing and wagging modes. We present a simple nine atom molecular model to com pute these defect modes by assuming the hydrogen to be bound in the antibon ding position of the nearest Ga atom, resulting in a defect complex of C-3V symmetry. Group theoretical methods are employed to obtain the frequencies of the normal modes enabling precise identification of localised modes.