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Recombination at surface states in GaN

Published online by Cambridge University Press:  21 March 2011

M. A. Reshchikov ,
P. Visconti ,
K. M. Jones ,
H. Morkoç ,
C. W. Litton  and
R. J. Molnar
M. A. Reshchikov
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
P. Visconti
Affiliation:
Also with: Istituto per lo Studio di Nuovi Materiali per l'Elettronica, CNR, Via Arnesano, Lecce, Italy and INFM-Unitá di Lecce, Dipartimento di Ingegneria dell'Innovazione, University di Lecce, Lecce, Italy
K. M. Jones
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
H. Morkoç
Affiliation:
Virginia Commonwealth University, Richmond, VA 23284, U.S.A.
C. W. Litton
Affiliation:
MIT, Lincoln Laboratory, Lexington, MA 02420, U.S.A.
R. J. Molnar
Affiliation:
Air Force Research Laboratory, Wright Patterson AFB, OH 45433, U.S.A.
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Abstract

We have studied radiative and nonradiative recombination at surface states in GaN, including as-grown samples and those treated with acids or bases. The surface states manifested themselves in two ways: (i) a reversible increase of the photoluminescence (PL) intensity after ultraviolet (UV) illumination in vacuum and (ii) appearance of new PL bands after treatment with acid or base and subsequent exposure to air. It has been established that the GaN surface physi-sorbs species from air (presumably oxygen) which induce surface states acting as nonradiative recombination centers. It has been found that nonradiative recombination of photogenerated carriers via surface states comprises more than 70% of the recombination in some GaN samples. Another type of the surface state, which participates in radiative recombination, has been found in GaN samples with Ga polarity after brief etching of the surface with hot acid or base and subsequent exposure to air. In such samples, a broad PL band emerges in the blue region of the spectrum at low temperatures. The blue band has been attributed to transitions of photogenerated electrons from donors in the near-surface depletion region to the surface states introduced by the above-mentioned procedure. The changes in the GaN surface caused by etching were examined by atomic force microscopy. In some samples the blue band appeared even when no evidence of the layer etching was found except for quite shallow etch pits formed at dislocation sites. The emerging blue band can be related to the surface states formed on the a-planes of etch pits.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 680: Symposium E – Wide Bandgap Electronics , 2001 , E5.4
Copyright
Copyright © Materials Research Society 2001

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References

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