Published in J. Vac. Sci. Technol. B 19, 1619 (2001).

Silicon on GaN(0001) and (0001) Surfaces

C. D. Lee,* R. M. Feenstra,* A. L. Rosa,** J. Neugebauer,** and J. E. Northrup***
*Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
**Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
***Xerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA 94304


Surface reconstructions and adatom kinetics of silicon on GaN(0001) and (0001) surfaces are studied by scanning tunneling microscopy, electron diffraction and first-principles calculations. In the low silicon coverage regime a 2×2 structure is observed, and is interpreted in terms of a model consisting of a Ga adatom on a monolayer of 3Ga + 1 Si and a SiGa atom in the third layer. For high silicon coverage a 4×4 structure appears containing disordered, partially 2×2 and "1×1" domains. After annealing above 300 C the "1×1" region become dominant and the 4×4 region is seen only near step edges. It is concluded that the silicon adatoms tend to reside in subsurface sites on the Ga-polar surface. Surface morphology in the presence of Si is smooth for the (0001) surface but rough for the (0001) surface. This difference is attributed to the presence of multiple Ga surface layers in the former case, which enhance surface diffusivities.

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