Real-time growth study of plasma assisted atomic layer epitaxy of InN films by synchrotron x-ray methods
The temporal evolution of high quality indium nitride (InN) growth by plasma-assisted atomic layer epitaxy (ALEp) on a-plane sapphire at 200 and 248 °C was probed by synchrotron x-ray methods. The growth was carried out in a thin film growth facility installed at beamline X21 of the National Synchro...
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Veröffentlicht in: | Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vacuum, surfaces, and films, 2017-05, Vol.35 (3) |
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Sprache: | eng |
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Zusammenfassung: | The temporal evolution of high quality indium nitride (InN) growth by
plasma-assisted atomic layer epitaxy (ALEp) on a-plane sapphire at 200 and 248 °C was probed by synchrotron x-ray
methods. The growth was carried out in a thin film growth facility installed at beamline X21 of the
National Synchrotron Light Source at Brookhaven National Laboratory and at beamline G3 of
the Cornell High Energy Synchrotron Source, Cornell University. Measurements of grazing
incidence small angle x-ray
scattering (GISAXS) during the initial cycles of growth revealed a
broadening and scattering near the diffuse specular rod and the development of
scattering
intensities due to half unit cell thick nucleation islands in the Yoneda wing with
correlation length scale of 7.1 and 8.2 nm, at growth temperatures (Tg) of 200
and 248 °C, respectively. At about 1.1 nm (two unit cells) of growth thickness
nucleation islands coarsen, grow, and the intensity of correlated
scattering peak
increased at the correlation length scale of 8.0 and 8.7 nm for Tg = 200 and
248 °C, respectively. The correlated peaks at both growth
temperatures can be fitted with a single peak Lorentzian function, which support single
mode growth. Post-growth in situ x-ray
reflectivity measurements indicate a growth rate of ∼0.36 Å/cycle consistent with
the growth rate previously reported for self-limited InN growth in a
commercial ALEp reactor. Consistent with the in situ GISAXS
study, ex situ
atomic force
microscopy power spectral density measurements also indicate single mode
growth. Electrical characterization of the resulting film revealed an
electron mobility of 50 cm2/V s for a 5.6 nm thick InN film on a-plane
sapphire, which
is higher than the previously reported mobility of much thicker InN films grown at higher
temperature by molecular beam epitaxy directly on sapphire. These early results indicated that in situ synchrotron x-ray study of the epitaxial
growth kinetics of InN films is a very powerful method to understand
nucleation and growth mechanisms of ALEp to enable
improvement in material quality and broaden its application. |
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ISSN: | 0734-2101 1520-8559 |
DOI: | 10.1116/1.4978026 |