APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011;
Dallas, Texas
Abstract: W3.00003 : The Electronic Properties of Native Point Defects at ZnO Surfaces and Interfaces
12:27 PM–1:03 PM
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Despite nearly sixty years of research, several fundamental
issues surrounding ZnO remain unresolved. Among the key
roadblocks to ZnO optoelectronics have been the difficulty of
p-type doping and the role of compensating native defects. Oxygen
vacancies (V$_{O})$, Zn interstitials (Zn$_{I})$, and residual
impurities such as H, Al, Ga, and In are reported
to be donors in ZnO, while Zn vacancies (V$_{Zn})$ are considered
to be acceptors. Electrically active complexes of V$_{O}$,
Zn$_{I}$, and V$_{Zn}$ can also exist. Although their impact on
free carrier compensation and recombination is recognized, the
physical nature of the donors and acceptors dominating carrier
densities in ZnO and their effects on carrier injection at
contacts is unresolved. The impact of these electronic states on
ZnO carriers at the nanoscale is only now being explored. We can
now address these issues using a combination of depth-resolved
and scanned probe techniques. Taken together, we clearly identify
the optical transitions and energies of V$_{Zn}$ and V$_{Zn}$
clusters, effects of annealing on their spatial distributions in
ion-implanted ZnO, and how V$_{Zn}$ and V$_{Zn}$ clusters modify
the near- and sub-surface carrier densities. Indeed, these native
point defects can directly impact the activation of extrinsic
dopants. We have now
discovered that nanostructures form spontaneously on
ZnO polar surfaces and create sub-surface V$_{Zn}$ locally
because of Zn diffusion that feeds the nanostructure growth.
Overall, this work reveals the interplay between ZnO electronic
defects, polarity, and surface nanostructure.
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[1] Y. Dong, F. Tuomisto, B. G. Svensson, A. Yu. Kuznetsov, and
L. J. Brillson, ``Vacancy defect and defect cluster energetics in
ion-implanted ZnO,'' Phys. Rev. B \textbf{81}, 081201(R)
(2010).\\[0pt]
[2] D. Doutt, H. L. Mosbacker, G. Cantwell,J. Zhang, J. J. Song,
and L. J. Brillson, ``Impact of near-surface defects and
morphology on ZnO luminescence,'' Appl. Phys. Lett. \textbf{94},
042111 (2009).
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.W3.3