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Effect of N/Ga Flux Ratio in GaN Buffer Layer Growth by MBE on (0001) Sapphire on Defect Formation in the GaN Main Layer

Published online by Cambridge University Press:  10 February 2011

S. Ruvimov
Affiliation:
Lawrence Berkeley National Laboratory, MS 63–203, Berkeley, CA 94720
Z. Liliental-Weber
Affiliation:
Lawrence Berkeley National Laboratory, MS 63–203, Berkeley, CA 94720
J. Washburn
Affiliation:
Lawrence Berkeley National Laboratory, MS 63–203, Berkeley, CA 94720
Y. Kim
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley, Berkeley, California, 94720
G. S. Sudhir
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley, Berkeley, California, 94720
J. Krueger
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley, Berkeley, California, 94720
E. R. Weber
Affiliation:
Department of Materials Science and Mineral Engineering, University of California at Berkeley, Berkeley, California, 94720
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Abstract

Transmission electron microscopy was employed to study the effect of N/Ga flux ratio in the growth of GaN buffer layers on the structure of GaN epitaxial layers grown by molecular-beamepitaxy (MBE) on sapphire. The dislocation density in GaN layers was found to increase from 1×1010 to 6×1010 cm−2 with increase of the nitrogen flux from 5 to 35 sccm during the growth of the GaN buffer layer with otherwise the same growth conditions. All GaN layers were found to contain inversion domain boundaries (IDBs) originated at the interface with sapphire and propagated up to the layer surface. Formation of IDBs was often associated with specific defects at the interface with the substrate. Dislocation generation and annihilation were shown to be mainly growth-related processes and, hence, can be controlled by the growth conditions, especially during the first growth stages. The decrease of electron Hall mobility and the simultaneous increase of the intensity of “green” luminescence with increasing dislocation density suggest that dislocation-related deep levels are created in the bandgap.

Type
Research Article
Copyright
Copyright © Materials Research Society 1999

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