Non-equilibrium Quantum Transport in Two Dimensional Electron Gases in Modulation Doped Heterostruvtures
2017-08
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Non-equilibrium Quantum Transport in Two Dimensional Electron Gases in Modulation Doped Heterostruvtures
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2017-08
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This thesis focuses on experimental investigations of transport in two dimensional electron gases (2DEG) driven out of equilibrium by microwaves and dc current. Part I presents the background information in four sections that describe the basics of magneto transport, Shubnikov-de Haas oscillations (SdHO), microwave-induced resistance oscillations (MIRO), and Hall field-induced resistance oscillations (HIRO). The second part of this thesis is broken into three sections that each discuss experimental findings of MIRO and HIRO in various 2DEGs. The fifth section discusses the observation of MIRO and HIRO in p-type Germanium quantum wells. This is significant because previous studies into a variety of different materials never showed any MIRO response. P-type Germanium is the second material for which MIRO and HIRO have been observed, making MIRO and HIRO not unique to GaAs quantum wells. The sixth section looks into the role of introducing alloy disorder into the quantum well on MIRO and HIRO. The quantum scattering rate was found to increase with the amount of alloy disorder and the MIRO prefactor that is decided by scattering times was not found to have a measurable change with increasing alloy disorder concentration. It was found the amplitude of HIRO is controlled by sharp disorder scattering contribution in mobility. The seventh section provides a systematic study into the effects of density on MIRO, which is not well understood. The analysis focuses on when one energy sub-band is populated, but also gives some observations of when two sub-bands are populated. When one sub-band is populated, increasing density was found to suppress the effective mass extracted from MIRO. The change in MIRO amplitude was found to be described by a combination of the zero-field resistance and the increase of quantum lifetime as density increased. When the second sub-band was populated, MIRO was found to be highly suppressed and this suppression cannot be explained by the MIRO mechanisms, quantum lifetime, or MIRO’s power factor.
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University of Minnesota Ph.D. dissertation.August 2017. Major: Physics. Advisor: Michael Zudov. 1 computer file (PDF); viii, 74 pages.
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Ebner, Quentin. (2017). Non-equilibrium Quantum Transport in Two Dimensional Electron Gases in Modulation Doped Heterostruvtures. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/191367.
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