AVS 56th International Symposium & Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThM

Paper EM-ThM2
Defect States in the Wide Gap Semiconducting Oxide Ga2O3

Thursday, November 12, 2009, 8:20 am, Room B1

Session: Oxide Semiconductors
Presenter: T.C. Lovejoy, University of Washington
Authors: T.C. Lovejoy, University of Washington
S. Zheng, University of Washington
E.G. Villora, National Institute for Materials Science, Japan
K. Shimamura, National Institute for Materials Science, Japan
F.S. Ohuchi, University of Washington
M.A. Olmstead, University of Washington
Correspondent: Click to Email

Ga2O3 is a transparent wide gap semiconducting oxide with potential applications as a transparent conductive oxide (TCO) or phase change memory (PCM) materials system. The mechanism for conductivity in this material is still under debate. The long established picture involves conduction by oxygen vacancy defect states, but unintentional silicon doping may also contribute. A recent paper [Appl. Phys. Lett. 92 202120 (2008)] shows the conductivity can be intentionally controlled over three orders of magnitude by silicon doping on the order of typical Si impurity levels in Ga2O3 source materials. In light of this, the actual role of oxygen vacancies is unclear. We illuminate this issue by studying separately the contribution to the electronic density of states of single crystal β-Ga2O3 by intentional silicon doping and oxygen deficiency with X-ray photoemission spectroscopy (XPS). Ar+ ion sputtering is an effective means of reduction that causes states to appear above the valence band maximum, which disappear on subsequent annealing. We demonstrate qualitative agreement with previously published density functional theory results [Nature Materials 7 391 (2008)] on the effect of oxygen deficiency in Ga2O3. Forthcoming hard x-ray photoemission and transport measurements will further elucidate this issue.