Atomic Ordering in InGaN Alloys within Nanowire Heterostructures.
Ternary III-nitride based nanowires (NWs) are promising for optoelectronic applications by offering advantageous design and control over composition, structure, and strain. Atomic-level chemical ordering in wurtzite InGaN alloys along the c-plane direction with a 1:1 periodicity within InGaN/GaN NW heterostructures was investigated by scanning transmission electron microscopy. Atomic-number-sensitive imaging contrast was used to simultaneously assign the In-rich and Ga-rich planes and determine the crystal polarity to differentiate unique sublattice sites. The nonrandom occupation of the c-planes in the InGaN alloys is confirmed by the occurrence of additional superlattice spots in the diffraction pattern within the ternary alloy. Compositional modulations in the ordered InGaN was further studied using atomic-resolution elemental mapping, outlining the substantial In-enrichment. Confirming the preferential site occupation of In-atoms provides experimental validation for the previous theoretical model of ordered InGaN alloys in bulk epilayers based on differences in surface site energy. Therefore, this study strongly suggests that atomic ordering in InGaN has a surface energetics-induced origin. Optimization of atomic ordering, in particular in III-nitride NW heterostructures, could be an alternative design tool toward desirable structural and compositional properties for various device applications operating at longer visible wavelengths.
Department of Materials Science and Engineering, McMaster University , Hamilton, Ontario L8S 4L7, Canada.|Brockhouse Institute for Materials Research and Canadian Centre for Electron Microscopy, McMaster University , Hamilton, Ontario L8S 4M1, Canada.
Steffi Y
SY
Woo
Department of Materials Science and Engineering, McMaster University , Hamilton, Ontario L8S 4L7, Canada.|Brockhouse Institute for Materials Research and Canadian Centre for Electron Microscopy, McMaster University , Hamilton, Ontario L8S 4M1, Canada.
Matthieu
M
Bugnet
Department of Electrical and Computer Engineering, McGill University , Montreal, Quebec H3A 0E9, Canada.
Hieu P T
HP
Nguyen
Department of Electrical and Computer Engineering, McGill University , Montreal, Quebec H3A 0E9, Canada.
Zetian
Z
Mi
Department of Materials Science and Engineering, McMaster University , Hamilton, Ontario L8S 4L7, Canada.|Brockhouse Institute for Materials Research and Canadian Centre for Electron Microscopy, McMaster University , Hamilton, Ontario L8S 4M1, Canada.
Gianluigi A
GA
Botton
InGaN; cation ordering; nanowire; quantum dot; scanning transmission electron microscopy (STEM)