Surface characterization of Ga-doped ZnO layers

Joy Dorene McNamara, J. D. Ferguson, M. Foussekis, I. Ruchala, M. A. Reshchikov, A. A. Baski, H. Liu, V. Avrutin, H. Morkoç

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations

Abstract

Epitaxial ZnO layers heavily doped with Ga (GZO) were grown at 400°C under metal-and oxygen-rich conditions in terms of metal-to-reactive oxygen ratio by plasma-assisted molecular beam epitaxy (MBE). Several atomic force microscopy (AFM) techniques were used to characterize the surface morphology and electrical properties of these GZO films in ambient conditions. Local I-V spectra indicate that layers grown under both O-rich and metal-rich conditions are highly resistive until a relatively high voltage sweep (±12 V) is used. After removal of an insulating surface layer, conduction is possible at lower voltages, but eventually the film resistivity increases and it again becomes insulating. In addition to local I-V spectra, local charge injection and subsequent surface potential measurements were used to probe surface charging characteristics. For charge injection experiments, a reverse-bias voltage is applied to the sample while scanning in contact mode with a metallized tip. The resultant change in surface potential due to trapped charge is subsequently observed using scanning Kelvin probe microscopy (SKPM). The layers deposited in a metal-rich environment demonstrate the expected behavior, but the O-rich layers show anomalous negative and positive charging. Finally, surface photovoltage (SPV) measurements using above-bandgap UV illumination were performed. The GZO layers produce SPV values of 0.4 to 0.5 eV, where the films deposited in an O-rich environment have slightly higher SPV values and faster restoration.

Original languageEnglish (US)
Title of host publicationTransparent Conducting Oxides and Applications
Pages77-82
Number of pages6
DOIs
StatePublished - Jan 1 2012
Event2010 MRS Fall Meeting - Boston, MA, United States
Duration: Nov 29 2010Dec 3 2010

Publication series

NameMaterials Research Society Symposium Proceedings
Volume1315
ISSN (Print)0272-9172

Other

Other2010 MRS Fall Meeting
CountryUnited States
CityBoston, MA
Period11/29/1012/3/10

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ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

McNamara, J. D., Ferguson, J. D., Foussekis, M., Ruchala, I., Reshchikov, M. A., Baski, A. A., Liu, H., Avrutin, V., & Morkoç, H. (2012). Surface characterization of Ga-doped ZnO layers. In Transparent Conducting Oxides and Applications (pp. 77-82). (Materials Research Society Symposium Proceedings; Vol. 1315). https://doi.org/10.1557/opl.2011.722