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Excitons bound to surface defects in GaN

Published online by Cambridge University Press:  11 February 2011

M. A. Reshchikov ,
D. Huang  and
H. Morkoç
M. A. Reshchikov
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
D. Huang
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
H. Morkoç
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
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Abstract

Sharp intense peaks are sometimes detected in the low-temperature photoluminescence (PL) spectrum of undoped GaN samples in the photon energy range of 3.0 – 3.46 eV. Some of these peaks can be attributed to excitons bound to dislocations and inversion domains, whereas some others originate from the GaN surface because they can be affected essentially by surface treatment. In our samples, grown by molecular beam epitaxy on sapphire substrate, the 3.42 eV peak always disappeared after removing the surface layer by etching for a few seconds in hot phosphoric acid. Atomic force microscopy images confirmed that such light etching modifies the surface morphology, although the etched depth is negligibly small. Moreover, intensities of two other peaks (at 3.32 and 3.35 eV) were observed to depend on sample etching, as well as on the length of subsequent exposure to air. The 3.32 and 3.35 eV peaks evolved with time of UV illumination, increasing by several times and demonstrating memory effect at low temperature. We attribute the 3.42 and 3.35 eV peaks to bound excitons, whereas the 3.32 eV peak is tentatively attributed to a surface donor-acceptor pair transition.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 743: Symposium L – GaN and Related Alloys , 2002 , L11.3
Copyright
Copyright © Materials Research Society 2003

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