Infrared spectroscopy of Mg-H local vibrational mode in GaN with polarized light

Magnesium-doped GaN grown by organometallic vapor phase epitaxy has been investigated by multitransmission infrared spectroscopy with the wave vector not along the c axis. This allows searching for local vibrational modes of complexes aligned along the c axis that cannot be seen by ``normal'' optical configuration. This technique, combined with polarized light, allows the precise determination of the geometry of the complexes. It has been found that the stable ``magnesium-hydrogen'' complex is not aligned along the c axis. The structure of this complex, including the angle between the electric dipole induced by the local mode and the c axis, has been determined. No other hydrogen-related complex aligned along the c axis has been detected.