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Electron Transport in High Aspect Ratio Semiconductor Nanowires and Metal-Semiconductor Interfaces

Sun, Zhuting
http://orcid.org/0000-0001-7765-2742
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479821421998919

Abstract Details

2016, PhD, University of Cincinnati, Arts and Sciences: Physics.
We are facing variability problems for modern semiconductor transistors due to the fact that the performances of nominally identical devices in the scale of 10~100 nm could be dramatically different attributed to the small manufacturing variations. Different doping strategies give statistical variations in the number of dopant atom density ND in the channel. The material size gives variations in wire diameter dW. And the immediate environment of the material leads to an additional level of variability. E.g. vacuum-semiconductor interface causes variations in surface state density Ds, metal-semiconductor interface causes variations in Schottky barrier and dielectric semiconductor interface induces dielectric confinement at small scales. To approach these variability problems, I choose Si-doped GaAs nanowires as an example. I investigate transport in Si-doped GaAs nanowire (NW) samples contacted by lithographically patterned Gold-Titanium films as function of temperature T. I find a drastically different temperature dependence between the wire resistance RW, which is relatively weak, and the zero bias resistance RC, which is strong. I show that the data are consistent with a model based on a sharp donor energy level slightly above the bottom of the semiconductor conduction band and develop a simple method for using transport measurements for estimates of the doping density after nanowire growth. I discuss the predictions of effective free carrier density neff as function of the surface state density Ds and wire size dW. I also describe a correction to the widely used model of Schottky contacts that improves thermodynamic consistency of the Schottky tunnel barrier profile and show that the original theory may underestimate the barrier conductance under certain conditions. I also provide analytical calculations for shallow silicon dopant energy in GaAs crystals, and find the presence of dielectrics (dielectric screening) and free carriers (Coulomb screening) cause a reduction of ionization energy and shift the donor energy level ED upward, accompanying conduction band EC shift downward due to band gap narrowing for doped semiconductor material. The theoretical results are in a reasonable agreement with previous experimental data. I also find that when the material reduces to nanoscale, dielectric confinement and surface depletion compete with both Coulomb screening and dielectric screening that shift the donor level ED down towards the band gap. The calculation should be appropriate for all types of semiconductors and dopant species.
Andrei Kogan, Ph.D. (Committee Chair)
Carlos Bolech, Ph.D. (Committee Member)
Howard Everett Jackson, Ph.D. (Committee Member)
Alexandre Sousa, Ph.D. (Committee Member)
137 p.
Condensation
GaAs; Nanowire; Schottky contact; Coulomb screening; surface depletion; dielectric confinement

Recommended Citations

Citations

  • Sun, Z. (2016). Electron Transport in High Aspect Ratio Semiconductor Nanowires and Metal-Semiconductor Interfaces [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479821421998919

    APA Style (7th edition)

  • Sun, Zhuting. Electron Transport in High Aspect Ratio Semiconductor Nanowires and Metal-Semiconductor Interfaces. 2016. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479821421998919.

    MLA Style (8th edition)

  • Sun, Zhuting. "Electron Transport in High Aspect Ratio Semiconductor Nanowires and Metal-Semiconductor Interfaces." Doctoral dissertation, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1479821421998919

    Chicago Manual of Style (17th edition)

ucin1479821421998919
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This open access ETD is published by University of Cincinnati and OhioLINK.