Relation between AI vacancies and deep emission bands in AIN epitaxial films grown by NH3-source molecular beam epitaxy

Intensity ratios of characteristic deep cathodoluminescence (CL) bands at 4.6, 3.8, and 3.1 eV to the near-band-edge emissions at 11 K of AlN epilayers grown by NH3-source molecular beam epitaxy were correlated with the change in the S parameter of positron annihilation measurement, which represents the concentration or size of Al vacancies (V-Al). Since the relative intensities of 3.1 and 3.8 eV bands increased remarkably with lowering supply ratio of NH3 to Al (V/III ratio) and growth temperature (T-g), they were assigned to originate from V-Al-O complexes. The V-Al concentration could be decreased by adjusting V/III ratio and T-g, resulting in observation of fine excitonic features in the CL spectra. From the energy separation between the ground and first excited states, the binding energy of A exciton was determined to be 48 meV. (c) 2007 American Institute of Physics.