Nearly defect-free InN microcrystals grown on Si(111) substrates were realized by plasma-assisted molecular beam epitaxy. High-resolution transmission electron microscope images reveal that these microcrystals exhibit single-crystalline wurtzite structure. Low temperature photoluminescence  exhibited a strong emission peak at 0.679eV with a very narrow line-width of 17meV at excitation power density of 3.4W/cm2. Temperature-dependent photoluminescence spectra follow the Varshni equation well, and peak energy blue-shifts by ~45meV from 300 to 15K. Power-density-dependent photoluminescence spectroscopy manifests direct near-band-edge transition. A low carrier density of 3 x 1017/cm3 was estimated from photoluminescence empirical relation, which was close to the critical carrier density of the Mott transition of 2 x 1017/cm3.

Photoluminescence Spectroscopy of Nearly Defect-Free InN Microcrystals Exhibiting Nondegenerate Semiconductor Behaviours. C.L.Hsiao, H.C.Hsu, L.C.Chen, C.T.Wu, C.W.Chen, M.Chen, L.W.Tu, K.H.Chen: Applied Physics Letters, 2007, 91[18], 181912