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Molecular Beam Epitaxy of Nonpolar Cubic AlxGa1−xN/GaN Epilayers

Published online by Cambridge University Press:  01 February 2011

Donat As
Affiliation:
d.as@uni-paderborn.de, University of Paderborn, Department of Physics, Warburger Str. 100, Paderborn, 33098, Germany, +495251605838, +495251605843
Stefan Potthast
Affiliation:
Potthast-Stefan@web.de, University of Paderborn, Department of Physics, Warburger Str. 100, Paderborn, 33098, Germany
Joerg Schoermann
Affiliation:
joergs@zitmail.uni-paderborn.de, University of Paderborn, Department of Physics, Warburger Str. 100, Paderborn, 33098, Germany
Elena Tschumak
Affiliation:
elena.tschumak@uni-paderborn.de, University of Paderborn, Department of Physics, Warburger Str. 100, Paderborn, 33098, Germany
Marcio F. de Godoy
Affiliation:
mgodoy@ifi.unicamp.br, University of Paderborn, Department of Physics, Warburger Str. 100, Paderborn, 33098, Germany
Klaus Lischka
Affiliation:
lischka@upb.de, University of Paderborn, Department of Physics, Warburger Str. 100, Paderborn, 33098, Germany
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Abstract

Cubic AlxGa1-xN films were grown by molecular beam epitaxy on freestanding 3C-SiC (001) substrates with an Al mole fraction of x=0 to 0.74. Using the intensity of a reflected high energy electron beam as a probe we find optimum growth conditions of c-AlGaN when a one-monolayer gallium coverage is formed at the growing surface. Clear reflection high energy electron diffraction oscillations during the initial growth of AlxGa1-xN/GaN layers were observed. The growth rate was about 177 nm/h. We find that the aluminium mole fraction is only determined by the aluminium flux, and that the AlxGa1-xN growth rate is independent on the aluminium content. Atomic force microscopy exhibits smooth surfaces with a RMS roughness of about 5 nm on 5×5 µm2 areas. Cathodoluminescence spectroscopy revealed clear band edge emission up to an aluminium mole fraction of x=0.52, showing a linear relation between the band gap energy and the Al composition.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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