Published in Phys. Rev. Lett. 85, 1902 (2000).
Spontaneous Formation of Indium-rich Nanostructures on InGaN(0001)
Huajie Chen,* R. M. Feenstra,* J. E. Northrup**, T. Zywietz*** and J. Neugebauer***
*Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
**Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA 94304
***Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg
4-6, D-14195 Berlin, Germany
InGaN(0001) surfaces prepared by molecular beam epitaxy have been
studied using scanning tunneling microscopy and first principles total
energy calculations. Nanometer-size surface structures are observed
consisting of either vacancy islands or ordered vacancy rows. The
spontaneous formation of these structures is driven by significant
strain in the surface layers, and by the relative weakness of the In-N
bond compared to Ga-N. Theory indicates that In will preferentially
bind at the edges and interior of the structures, thereby giving rise
to an inhomogeneous In distribution at the surface. The vacancy
islands typically form a nearly uniform array with a separation of
about 5 nm, which is close to the observed length scale of
compositional fluctuations in InGaN alloys.
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