Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 17: Poster Ib
HL 17.19: Poster
Freitag, 4. März 2005, 16:30–19:00, Poster TU F
Analysis of a conducting channel at the ZnO surface using MOS structures — •Arnd Geis1, Oliver Schmidt1, Peter Kiesel1, Noble Johnson1, Andreas Waag2, Andrey Bakin2, and Gottfried Döhler3 — 1Palo Alto Research Center, 3333 Coyote Hill Rd., Palo Alto, CA 94304, USA — 2University of Braunschweig, Institute for Semiconductor Technology, Hans-Sommer Str. 66, 38106 Braunschweig — 3University of Erlangen, Institute for Technical Physics I, Erwin Rommel-Str. 1, 91058 Erlangen
The electrical properties of high-resistivity zinc oxide (ZnO) are strongly influenced by the sample ambient. Bulk samples that have been high resistive in ambient air can be reversibly transferred into a high conducting state under vacuum.
As an explanation we proposed a conducting electron channel at the ZnO surface. Under vacuum this channel appears upon annealing. Exposure to ambient air destroys the channel. The channel is evident only for samples showing a high bulk resistivity, and it seems to be the "natural" state of the ZnO surface.
We have investigated a variety of surface passivation layers and coatings in order to preserve or avoid the surface conducting channel under either environment. Appropriate coatings that preserve the surface conducting channel have been used for fabrication of MOS structures. We investigated the nature of the conducting channel by modulating the free carrier concentration at the surface. Our findings are important with regard to MOSFET devices based on ZnO.