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


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
Number of pages6
StatePublished - 2012
Event2010 MRS Fall Meeting - Boston, MA, United States
Duration: Nov 29 2010Dec 3 2010

Publication series

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


Other2010 MRS Fall Meeting
Country/TerritoryUnited States
CityBoston, MA

ASJC Scopus subject areas

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


Dive into the research topics of 'Surface characterization of Ga-doped ZnO layers'. Together they form a unique fingerprint.

Cite this