Journal
JOURNAL OF CRYSTAL GROWTH
Volume 451, Issue -, Pages 65-71Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jcrysgro.2016.06.055
Keywords
Growth models; Surface kinetics; Metalorganic chemical vapor deposition; Nitrides
Funding
- NSF [DMR-1108071, DMR-1312582, DMR-1508191, ECCS-1508854]
- ARL [W911QX-10-C-0027]
- ARO [W911NF-14-C-0008]
- AFOSR National Defense Science and Engineering Graduate (NDSEG) fellowship [32CFR168a]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1312582] Funding Source: National Science Foundation
- Directorate For Engineering
- Div Of Electrical, Commun & Cyber Sys [1508854] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [1508191] Funding Source: National Science Foundation
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Metal-polar, Al-rich AlGaN films were grown on both single crystalline AlN and sapphire substrates. The role of surface morphology and surface kinetics on AlGaN composition is presented. With the reduced dislocation density of the films grown on AlN substrates, atomically smooth bilayer stepped surfaces are achieved with RMS roughness of less than 50 pm for a 5 x 51.mu m(2) AFM scan area. By controlling the surface supersaturation through adjusting the growth rate, a transition from 2D nucleation to step flow was observed. The critical misorientation angle for step-bunching in nominal Al0.70Ga0.30N grown with a growth rate of 600 nm/h on AlN substrates was found to be 0.4 degrees. The composition of bilayer stepped AlGaN was strongly dependent on substrate misorientation angle, where a compositional variation by a factor of two for a change in misorientation angle from 0.05 to 0.40 degrees was observed; this is explained by the different surface diffusion lengths of Ga and Al. Step-bunching resulted in strong compositional inhomogeneity as observed by photoluminescence and scanning transmission electron microscopy studies. (C) 2016 Elsevier B.V. All rights reserved.
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