C-axis oriented InN nanocolumns (NCs) were grown on (0 0 0 1) GaN templates by molecular beam epitaxy. In situ spectroscopic ellipsometry and reflection high-energy electron diffraction demonstrated that InN NCs epitaxy was initiated from self-organized growth of InN quantum dots in Stranski-Krastanov mode, which was further confirmed by ex situ measurement of atomic force microscopy. InN NCs were of high crystal quality. The full-width at half-maximum (FWHM) value of omega-scan for (002) InN NCs showed a comparative value with that of GaN template in a range of 500-600 arcsec. (c) 2006 Elsevier B.V. All rights reserved.