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Materials Science Division |
HighlightsCharacterizing High-performance Nanorod-array LEDsCharacterizing High-performance Nanorod-array LEDs Scientific Achievement The InGaN materials systems provides a potential route to creating effective LEDs in the green range of emission. Increased InN incorporation should push the wavelength up from the ~500 nm currently available. One of the road-blocks to creating such a device is the immiscibility of InN and GaN under standard conditions. In this work, InGaN is grown through a porous dielectric mask, creating an array of nanorods capped with hexagonal pyramids. Strain relief at the facets and apex of these pyramids should allow for the incorporation of a higher concentration of InN. To characterize these structures, site specific analysis of the InN concentration is necessary. STEM-EDS was utilized at the EMC to obtain profiles along the length of graded nanorod-pyramid structures. The presence of InN was confirmed, along with a general trend of increasing indium signal along the length of the nanorod. The characterization of the pyramid was limited by geometry and sample preparation issues, but did suggest a significant presence of InN. Additionally, the STEM and EDS data evidenced the inhomogeneity of the nanorod. Significance The STEM and EDS data were able to confirm the presence of InN in the nanorod and pyramid caps, allowing the observed emission of these devices to be correlated to the nanorod-pyramid structures. The results also indicated that more work on the graded growth is needed to achieve a continuous gradient. Furthermore, sample preparation issues were diagnosed in these experiments, in regards specifically to producing FIB-liftout samples suitable for EDS analysis of InGaN. Improved preparation methods have been incorporated into current work, and EDS of future graded-InGaN nanorod-pyramids should be freer of artifacts and easier to analyze quantitatively. Performers 
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