Local vibrational modes of the Mg-H acceptor complex in GaN

Local vibrational modes (LVMs) are reported for Mg-doped GaN grown by metalorganic chemical vapor deposition. Hetero-epitaxial layers of GaN:Mg, either as-grown, thermally activated, or deuterated, were investigated with low-temperature, Fourier-transform infrared absorption spectroscopy. The as-grown material, which was semi-insulating, exhibits a LVM at 3125 cm(-1). Thermal annealing increases the p-type conductivity, as established with Hall effect measurements, and proportionally reduces the intensity of this LVM. Deuteration of the activated material creates a LVM at 2321 cm(-1). The isotopic shift establishes the presence of hydrogen in the vibrating complex. The new LVMs are assigned to the stretch modes of the Mg-H and Mg-D complexes in GaN, with the vibrational frequencies indicative of a strong N-H bond as recently proposed from total-energy calculations. (C) 1996 American Institute of Physics.