Preparation of stoichiometric GaN(0001)-1x1: an XPS study
S.M. Widstrand, K.O. Magnusson, L.S.O. Johansson, E. Moons, M. Gurnett
Karlstad University, Materials Physics, Universitetsgatan 2, 651 88 Karlstad, Sweden
H.W. Yeom
Yonsei University, Center for Atomic Wires and Layers Institute of Physics and Applied Physics, 134 Shinchon, Seoul 120-749, Korea
H. Miki
Showa Denko KK, Chichibu Research Labarotory, Central Research Laboratory, 1505 Shimokagemori, Chichibu-shi, Saitama 369-1871, Japan
M. Oshima
University of Tokyo, Department of Applied Chemistry, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
This article was received on Wednesday, January 21, 2004 and
accepted on Friday, April 16, 2004. Abstract
We
report on the investigation of GaN(0001)-1x1 using synchrotron radiation
x-ray excited photoelectron spectra from the core levels Ga 3p and N 1s, as
well as from the contaminants O 1s and C 1s. Measurements were done after
outgassing (a) and during three surface treatment methods performed in
sequence; (b) ammonia (NH3) flux anneals, (c) Ga deposition with
sample held at room temperature followed by vacuum anneal, and (d) Ga
deposition on a heated sample followed by Ga desorption during NH3
flux anneal. We have found that the initial NH3 flux anneals
increased the amount of present N on the surface and enabled the formation of a
well-ordered surface structure, according to the low energy electron
diffraction (LEED) pattern. After treatment (b) and (d) the core level spectra
of Ga 3p are much improved showing clearly distinct features indicative of
increased Ga-N bonding. The Ga to N concentration ratio decreases during the
surface treatments from 4.0 to 1.1, hence towards stoichiometry. The amounts of
C (and O) present on the surface after outgassing corresponded to 1.1 (0.9)
monolayers (ML) but reduced to 0.1 (0.1) ML after the final treatment (d). The
Fermi level position in the band gap shifts down by 0.55 eV during the surface
treatments, indicating a change of states present in the band gap. We have also
found strong support that this Ga-polar sample is initially
Ga-terminated.Outline
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 9, 4(2004).
last updated Tuesday, October 18, 2005 1:33:16 PM.© 2004-2005 The Materials Research Society
