@article{ef8eefe3c23041448268d9828ba72357,
title = "Effect of polarity on the growth of InN films by metalorganic chemical vapor deposition",
abstract = "The effect of surface polarity on InN growth on GaN by metalorganic chemical vapor deposition (MOCVD) was investigated. The polarity of the InN was found to follow that of the initial GaN template as determined by a comparison of experimental and simulated convergent beam electron diffraction patterns. Under identical MOCVD growth conditions, In-polar InN was observed to nucleate and grow on Ga-polar GaN as pyramidal-shaped islands with (10 1- 1) as the stable surface facet. In contrast, enhanced lateral growth and reduced surface roughness were observed for N-polar InN grown on N-polar GaN. InN films grown on (0001) sapphire substrates using a thin AlN buffer under identical conditions to those used for growth on the GaN templates also exhibited reduced surface roughnesses and were determined to be N polar. A qualitative model based on the difference in surface terminations and crystal structures is proposed to explain the observed differences in the structural properties and growth modes of the In-polar and N-polar InN films.",
author = "Abhishek Jain and Xiaojun Weng and Srinivasan Raghavan and Vanmil, {Brenda L.} and Thomas Myers and Redwing, {Joan M.}",
note = "Funding Information: Financial support for this project was provided by the National Science Foundation (Grant Nos. ECS-0093742 and DMR-0606451). TEM work was performed in the electron microscopy facility of the Penn State node of the NSF National Nanotechnology Infrastructure Network (Grant No. 0335765). Table I. Representative x-ray rocking curve ( ω -scan) FWHM values for N-polar and Ga-polar GaN templates and InN films grown on the different buffer layers/templates. Buffer/template description ω -FWHM (0002) GaN(deg) ω -FWHM (0002) InN(deg) ω -FWHM ( 10 1 ¯ 1 ) InN(deg) LT-AlN N/A 0.39 0.84 N-polar GaN 0.2 0.32 0.43 Ga-polar GaN 0.1 0.22 0.53 FIG. 1. Notation for InN polarity based on bond orientation: (a) with three of the dangling bonds on the In atom pointing toward the substrate, the film is In polar, and (b) with three of the dangling bonds on the In atom pointing away from the substrate, the film is N polar. FIG. 2. Cross-sectional TEM images and corresponding CBED patterns (experimental and simulated) for GaN templates grown by (a) HVPE and (b) MBE. FIG. 3. SEM images showing surface morphology of InN grown on (a) LT-AlN, (b) N-polar GaN, and (c) Ga-polar GaN. Cross-sectional FE-SEM images of the interface between InN and (d) LT-AlN, (e) N-polar GaN, and (f) Ga-polar GaN. FIG. 4. Cross-sectional TEM images and corresponding CBED pattern comparison with the simulated CBED patterns (using the JEMS software) for InN grown on (a) N-polar GaN template, (b) Ga-polar GaN template, and (c) LT-AlN buffer. FIG. 5. (a) Cross-sectional HRTEM image of In-polar InN along with (b) low-resolution image and (c) FFT showing orientation of the island facet to be ( 10 1 ¯ 1 ) . FIG. 6. Surface morphology evolution with growth time of [(a)–(d)] N-polar InN on LT-AlN and [(e)–(h)] In-polar InN on Ga-polar GaN. Note the difference in nucleus densities in (a) and (e). Scale bar equals 2 μ m . FIG. 7. Schematic of proposed growth mechanism of N-polar InN under N-rich conditions: (b) shows the subsequent growth surface after indium incorporation on (a). Dashed lines mark the step on the ( 000 1 ¯ ) growth surface. FIG. 8. Schematic of proposed growth mechanism of In-polar InN under N-rich conditions: (a)–(c) are subsequent steps during indium incorporation on the growth surface. Dashed lines mark the step on the ( 10 1 ¯ 1 ) growth surface. ",
year = "2008",
doi = "10.1063/1.2973681",
language = "English (US)",
volume = "104",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics",
number = "5",
}