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Measurement of Small Size Effects at Metal/Nanostructure Schottky contacts

Speaker: Jon P. Pelz, Ohio State University
Date & Time: August 29, 2005 - 12:00pm
Location: Serin Third Floor Seminar Room – 385E

Measurement of Small Size Effects at Metal/Nanostructure Schottky contacts
Laboratory for Surface Modification

Jon P. Pelz, Ohio State University
12 Noon – Serin Third Floor Seminar Room – 385E

There is great interest in making electronic devices using semiconductor nanostructures, but to date there has been little work to understand how carrier transport through the contacts to the nanostructures are influenced by small-size effects, such as quantum-confinement and local geometry-induced fields. To image and quantify these small-size effects, we have made direct, nm-resolution electronic measurements and finite-element electrostatic calculations of a model metal/semiconductor-nanostructure system in which the nanostructure dimension can be systematically varied down to ~1 nm. The measurement technique is cross-sectional ballistic electron emission microscopy (XBEEM) of cleaved GaAs quantum well (QW) heterostructures [1], and of unique self-forming quantum wells in SiC [2,3].
We find that the Schottky barrier height over metal/GaAs-QW nanocontacts systematically increases with decreasing QW width, by up to ~140 meV for a 1nm-wide QW. This is mostly due to a large quantum-confinement increase (~200 meV) of the QW conduction band minimum, modified by smaller decreases due to “environmental” electrostatic effects from the surrounding metal/AlGaAs interface. Even larger quantum-confinement increases (up to ~680 meV) are observed at metal/SiC-QW nanocontacts. Time permitting, I will discuss on-going measurements to directly image and quantify lateral hot-electron spreading in the metal film, and local electron scattering from defects located below the metal/SiC interface. Work Supported by NSF and ONR.

[1] C. Tivarus et al., Phys. Rev. Lett. 94, 206803 (2005).
[2] Y. Ding et al., Phys. Rev. B69, (2004), 041305(R).
[3] K.-B . Park et al., Appl. Phys. Lett. 86, 222109 (2005).

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