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Epitaxial c-GaAs/h-GaN Heterostructures

Published online by Cambridge University Press:  01 February 2011

Vladimir Chaldyshev
Affiliation:
[email protected], Ioffe Institute, Politekhnicheskaya 26, St. Petersburg, N/A, 194021, Russian Federation, 7-812-247-9393, 7-812-247-1017
Yurii Musikhin
Affiliation:
[email protected], Ioffe Institute
Nikolai Bert
Affiliation:
[email protected], Ioffe Institute
Bent Nielsen
Affiliation:
[email protected], SUNY Stony Brook, United States
Emilio Mendez
Affiliation:
[email protected], SUNY Stony Brook, United States
Zhixun Ma
Affiliation:
[email protected], Brooklyn College of CUNY, United States
Todd Holden
Affiliation:
[email protected], Brooklyn College of CUNY, United States
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Abstract

GaAs/GaN heterostructures were grown by molecular-beam epitaxy using GaN/supphire (0001) templates. In spite of a ∼20% lattice mismatch, epitaxial growth was realized, so that the GaAs films showed good adhesion and their surface had a large mirror-like area. The GaAs films were as thick as 1um. The surface profile was characterized by atomic-force microscopy, which gave an average roughness of 10 nm for a 5×5 μm scan. Micro-Raman characterization and transmission electron microscopy (TEM) showed that the epitaxial GaAs films had zincblende lattice with (111) orientation, whereas the GaN substrates had wurtzite symmetry. The GaAs/GaN interface was found to be flat and abrupt. A large number of defects have been observed which originated from relaxation of the large lattice mismatch. The defects included misfit dislocations and nanocavities at the interface, as well as dislocations and stacking faults in the bulk of the GaAs film. Sharp interference fringes and characteristic behavior were observed for the ψ and Δ parameters of spectroscopic ellipsometry in the range of 0.75-5.3 eV. Simulation of the optical properties of the GaAs/GaN/sapphire heterostructure indicated a reasonably good optical quality of the layers and interfaces. Photoluminescence (PL) spectra recorded at the temperatures from 17 to 300 K revealed wide and weak radiative bands. Non-radiative processes dominated in recombination of non-equilibrium carriers. The observed PL broadening originated from the band tails that were a result of the high density of charged defects.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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References

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