8 March 2014 The formation of hexagonal-shaped InGaN-nanodisk on GaN-nanowire observed in plasma source molecular beam epitaxy
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Abstract
We report on the properties and growth kinetics of defect-free, photoluminescence (PL) efficient mushroom-like nanowires (MNWs) in the form of ~30nm thick hexagonal-shaped InGaN-nanodisk on GaN nanowires, coexisting with the conventional rod-like InGaN-on-GaN nanowires (RNWs) on (111)-silicon-substrate. When characterized using confocal microscopy (CFM) with 458nm laser excitation, while measuring spontaneous-emission at fixed detection wavelengths, the spatial intensity map evolved from having uniform pixelated emission, to having only an emission ring, and then a round emission spot. This corresponds to the PL emission with increasing indium composition; starting from emission mainly from the RNW, and then the 540 nm emission from one MNWs ensemble, followed by the 590 nm emission from a different MNW ensemble, respectively. These hexagonal-shaped InGaN-nano-disks ensembles were obtained during molecular-beam-epitaxy (MBE) growth. On the other hand, the regular rod-like InGaN-on-GaN nanowires (RNWs) were emitting at a shorter peak wavelength of 490 nm. While the formation of InGaN rod-like nanowire is well-understood, the formation of the hexagonal-shaped InGaN-nanodisk-on-GaN-nanowire requires further investigation. It was postulated to arise from the highly sensitive growth kinetics during plasma-assisted MBE of InGaN at low temperature, i.e. when the substrate temperature was reduced from 800 °C (GaN growth) to <600 °C (InGaN growth), during which sparsely populated metal-droplet formation prevails and further accumulated more indium adatoms due to a higher cohesive bond between metallic molecules.
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Tien Khee Ng, Tien Khee Ng, Anwar Gasim, Anwar Gasim, Dongkyu Cha, Dongkyu Cha, Bilal Janjua, Bilal Janjua, Yang Yang, Yang Yang, Shafat Jahangir, Shafat Jahangir, Chao Zhao, Chao Zhao, Pallab Bhattacharya, Pallab Bhattacharya, Boon Siew Ooi, Boon Siew Ooi, } "The formation of hexagonal-shaped InGaN-nanodisk on GaN-nanowire observed in plasma source molecular beam epitaxy", Proc. SPIE 8986, Gallium Nitride Materials and Devices IX, 898613 (8 March 2014); doi: 10.1117/12.2039627; https://doi.org/10.1117/12.2039627
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