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On the presence of Ga2O sub-oxide in high-pressure water vapor annealed AlGaN surface by combined XPS and first-principles methods

Authors
  • Escaño, Mary Clare S.1
  • Asubar, Joel T.2
  • Zenji Yatabe3
  • David, Melanie Y.4
  • Uenuma, Mutsunori5
  • Tokuda, Hirokuni2
  • Uraoka, Yukiharu5
  • Kuzuhara, Masaaki2
  • Tani, Masahiko1
Type
Published Article
Journal
Applied Surface Science
Publisher
Elsevier
Publication Date
Jul 04, 2019
Volume
481
Identifiers
DOI: 10.1016/j.apsusc.2019.03.196
Source
MyScienceWork
License
White

Abstract

We conducted X-ray photoelectron spectroscopy (XPS) and first-principles calculations based on density functional theory (DFT) to confirm the presence of Ga2O sub-oxide in high-pressure water vapor annealed AlGaN surface. We note that the Ga 3d XPS peak broadens and shifts towards higher binding energies, which suggests surface oxide formation. Deconvoluted Ga 3d XPS profiles between HPWVA-treated and reference samples reveal reasonable inclusion of Ga2O peak, suggesting formation of Ga2O sub-oxide. To theoretically confirm the presence of Ga2O, we calculated the Ga 3d core-level shift using initial state approximation. We obtained a 0.74 eV shift, in reasonable agreement with that of Ga2O. Moreover, based on the calculation of net charge on Ga using DFT, we also obtained a +1 oxidation state for Ga, indicating its existence in Ga2O form. By combining theory and experiment, therefore, we have explored the possibility of the formation of Ga2O sub-oxide, which may provide new avenues for obtaining highly stable operation in GaN-based devices.

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