Near-field optical spectroscopy and microscopy of self-assembled GaN/AlN nanostructures

Neogi, A.; Gorman, B. P.; Morkoç, H.; Kawazoe, T.; Ohtsu, M.
January 2005
Applied Physics Letters;1/24/2005, Vol. 86 Issue 4, p043103
Academic Journal
The spatial distribution and emission properties of small clusters of GaN quantum dots in an AlN matrix are studied using high-resolution electron and optical microscopy. High-resolution transmission electron microscopy reveals near vertical correlation among the GaN dots due to a sufficiently thin AlN spacer layer thickness, which allows strain induced stacking. Scanning electron and atomic force microscopy show lateral coupling due to a surface roughness of ∼50-60 nm. Near-field photoluminescence in the illumination mode (both spatially and spectrally resolved) at 10 K revealed emission from individual dots, which exhibits size distribution of GaN dots from localized sites in the stacked nanostructure. Strong spatial localization of the excitons is observed in GaN quantum dots formed at the tip of self-assembled hexagonal pyramid shapes with six [10&11macr;] facets.


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