Fermi level (FL) pinning at the Ge valence band results in a high Schottky barrier height for all metal/n-Ge contacts. The origin of this pinning effect has been ascribed to either metal induced gap states or surface states arise from the native defects at the Ge surface, such as dangling bonds. The discrepancy in the reported results/explanations is mainly due to the lack of an explicit characterization of a high quality metal/Ge or metal/ultrathin oxide/Ge junction, which should be ideally single crystalline, atomically smooth and free of process-induced defects or intermixing. We report the Schottky characteristics of high quality metal/MgO/n-Ge junctions with the ultrathin MgO epitaxially grown on Ge. We find the depinning effect displays a weak dependence on the MgO thickness, indicating the interface states due to the native defects on Ge surface are likely to play the dominant role in FL pinning.
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8 March 2010
Research Article|
March 08 2010
Investigating the origin of Fermi level pinning in Ge Schottky junctions using epitaxially grown ultrathin MgO films
Yi Zhou;
Yi Zhou
a)
1Department of Electrical Engineering, Device Research Laboratory,
University of California
, Los Angeles, California 90095, USA
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Wei Han;
Wei Han
2Department of Physics and Astronomy,
University of California
, Riverside, California 92521, USA
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Yong Wang;
Yong Wang
3School of Engineering and Center of Microscopy and Microanalysis,
The University of Queensland
, Brisbane QLD 4072, Australia
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Faxian Xiu;
Faxian Xiu
1Department of Electrical Engineering, Device Research Laboratory,
University of California
, Los Angeles, California 90095, USA
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Jin Zou;
Jin Zou
3School of Engineering and Center of Microscopy and Microanalysis,
The University of Queensland
, Brisbane QLD 4072, Australia
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R. K. Kawakami;
R. K. Kawakami
2Department of Physics and Astronomy,
University of California
, Riverside, California 92521, USA
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Kang. L. Wang
Kang. L. Wang
1Department of Electrical Engineering, Device Research Laboratory,
University of California
, Los Angeles, California 90095, USA
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a)
Electronic mail: yizhou@ee.ucla.edu.
Appl. Phys. Lett. 96, 102103 (2010)
Article history
Received:
September 29 2009
Accepted:
February 16 2010
Citation
Yi Zhou, Wei Han, Yong Wang, Faxian Xiu, Jin Zou, R. K. Kawakami, Kang. L. Wang; Investigating the origin of Fermi level pinning in Ge Schottky junctions using epitaxially grown ultrathin MgO films. Appl. Phys. Lett. 8 March 2010; 96 (10): 102103. https://doi.org/10.1063/1.3357423
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