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Electrical characterization of He+ irradiated n-ZnO

Michael Hayes 1Francois D. Auret 1Jacqueline M. Nel 1Werner Wesch 2Elke Wendler 2

1. University of Pretoria, Department of Physics, University str., Pretoria 0084, South Africa
2. Freidrich-Schiller-Universitat Jena, Jena 07743, Germany

Abstract

Due to its direct wide bandgap of 3.37eV, Zinc oxide (ZnO) has become the focus of many studies. Devices such as detectors, lasers and diodes operating in the ultra-violet (UV) and blue regions of the spectrum have been reported. It has previously been reported that the carrier removal rate in ZnO by MeV protons is almost two orders of magnitude lower than that in GaN. To investigate if this is due to a material property of the ZnO, or perhaps a case of radiation enhanced annealing, He+ irradiation were performed at room temperature as well as at low temperatures. ZnO Schottky barrier diodes (SBD's) were fabricated with 20/80/40/80 nm Ti/Al/Pt/Au ohmic contacts on the O face and circular 0.5 mm in diameter 500 nm thick Ru Schottky contacts in the Zn face. The carrier concentration of the ZnO prior to irradiation was approximately 5×1016 cm-3. These diodes were irradiated with 1.8 MeV He+ with fluences ranging from 1×1012 cm-2 to 5×1013 cm-2. Deep level transient spectroscopy (DLTS) was used to study the defects introduced. These measurements revealed that this implantation introduced a defect with an energy level at 0.54 eV below the conduction band. The introduction rate of this defect for 1.8 MeV He ions was calculated to be 220 cm-1. This appears to be the same defect that is introduced during proton implantation of ZnO.

 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2006, Symposium F, by Michael Hayes
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 06:27
Revised:   2009-06-07 00:44