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Photoluminescence study of deep-level defects in undoped GaN

Published online by Cambridge University Press:  21 March 2011

M. A. Reshchikov
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
H. Morkoç
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
S. S. Park
Affiliation:
Samsung Advanced Institute of Technology, P.O.Box 111, Suwon, Korea 440-600
K. Y. Lee
Affiliation:
Samsung Advanced Institute of Technology, P.O.Box 111, Suwon, Korea 440-600
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Abstract

We studied photoluminescence (PL) and PL excitation (PLE) spectra in a large number of undoped GaN layers grown on sapphire by molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD) and hydride vapor phase epitaxy (HVPE). The HVPE-grown GaN layers with thickness of ~200 m m were separated from the sapphire substrate by laser lift-off and represented bulk freestanding templates of very high quality. Identical position and shape of the YL band were reproduced in many samples grown by MBE and MOCVD: maximum at ~2.23 eV and full width at half maximum (FWHM) of about 460 meV at room temperature. However, in some samples the band maximum was observed at about 2.0 eV. The freestanding templates reveal a broad band (FWHM=530-680 meV) whose position depends on excitation energy and intensity, varying from 2.22 eV to 2.47 eV. PLE spectra taken from various samples represented a broad band with apparent maximum at about 3.3 eV. For below-gap excitation, the intensity of the YL band was independent of temperature except for the one in the freestanding template. The latter was temperature independent above 60 K, however at lower temperatures the PL intensity decreased by 5 times. An activation energy of 15 meV has been determined that is related to a barrier in the adiabatic potential in the excited state of the defect.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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