Intensity ratios of deep cathodoluminescence (CL) bands at 4.6, 3.8 and 3.1 eV to the near-band-edge emission of AlN epilayers grown by NH 3-source molecular beam epitaxy were correlated with the change in S parameter of positron annihilation measurement, which represents the concentration or size of Al vacancies (VAl). The origins of the deep emission bands were assigned to donor-acceptor pairs associated with V Al and/or VAl-defect complexes. The VAl concentration was decreased by adjusting the flux ratio of NH3 to Al and growth temperature, 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 free A-exciton was estimated to be 48 meV.
|Number of pages||4|
|Journal||Physica Status Solidi (C) Current Topics in Solid State Physics|
|Publication status||Published - 2008|
|Event||7th International Conference of Nitride Semiconductors, ICNS-7 - Las Vegas, NV, United States|
Duration: 2007 Sept 16 → 2007 Sept 21