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Electron transport and scattering in the 2DEG base hot-electron transistorJansen, Richard-Jan Engel January 1995 (has links)
No description available.
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Ultrafast Coherent Electron Spin Control and Correlated Tunneling Dynamics of Two-Dimensional Electron GasesPhelps, Carey E., 1982- 06 1900 (has links)
xvi, 143 p. : ill. (some col.) / Electron spins form a two-level quantum system in which the remarkable properties of quantum mechanics can be probed and utilized for many applications. By learning to manipulate these spins, it may be possible to construct a completely new form of technology based on the electron spin degree of freedom, known as spintronics. The most ambitious goal of spintronics is the development of quantum computing, in which electron spins are utilized as quantum bits, or qubits, with properties that are not possible with classical bits. Before these ideas can become reality, a system must be found in which spin lifetimes are long enough and in which spins can be completely controlled. Semiconductors are an excellent candidate for electron spin control since they can be integrated into on-chip devices and produced on a scalable level.
The focus of this dissertation is on electron spin control in two different semiconductor systems, namely a two-dimensional electron gas in a modulation-doped quantum well and donor-bound electrons in bulk semiconductors. Both systems have been studied extensively for a variety of purposes. However, the ability to manipulate spins has been elusive. In this dissertation, the first experimentally successful demonstration of electron spin control in a two-dimensional electron gas is presented, in which ultrafast optical pulses induce spin rotations via the optical Stark effect. Donor-bound electron spin manipulation in bulk semiconductors is also investigated in this dissertation. Important information was obtained on the limiting factors that serve to prohibit spin control in this system. By taking these new factors into account, it is our hope that full electron spin control can eventually be accomplished in this system.
Finally, through the course of investigating electron spin dynamics, a strange nonlinear optical behavior was observed in a bilayer system, which was determined to result from a coupling of optical interactions with tunneling rates between layers. The data suggest that there is a strong interplay between interlayer and intralayer correlations in this system. Investigations into the nature of this interaction were undertaken and are presented in the last part of this dissertation.
This dissertation includes previously published and unpublished co-authored material. / Committee in charge: Dr. Daniel Steck, Chair;
Dr. Hailin Wang, Advisor;
Dr. Jens Nockel, Inside;
Dr. John Toner, Inside;
Dr. Andrew Marcus,
Outside
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Polarization-discontinuity-doped two-dimensional electron gas in BaSnO3/LaInO3 heterostructures grown by plasma-assisted molecular beam epitaxyHoffmann, Georg 15 September 2023 (has links)
Die vorliegende Arbeit beschäftigt sich mit dem Wachstum von BaSnO3/LaInO3
(BSO/LIO) Schichten mittels Plasma-unterstützter Molekularstrahlepitaxie (PAMBE).
Für die Realisierung der BSO/LIO Heterostruktur müssen zuvor Wege für
ein stabiles Herstellungsverfahren sowohl der BSO als auch der LIO Schichten
gefunden werden. Aus diesem Grund beschäftigt sich der erste Teil dieser Arbeit
mit den Herausforderungen der Suboxidbildung und Suboxidquellen.
Das Wissen um Suboxide ist alt, aber es wurde bisher nicht stark in der Anwendung
der Oxid-MBE berücksichtig oder benutzt. Engagierte Studien werden in
dieser Arbeit durchgeführt, die zeigen, dass bei Suboxidquellen wie z.B. der Mischung
aus SnO2 und Sn sich die Einbaukinetik gegenüber einer elementaren
Quelle (z.B. Zinn) vereinfacht.
Die in dieser Arbeit herausgearbeitete
Effizienz der Mischquellen hat bereits dazu geführt, dass weitere Oxide wie
Ga2O3 und SnO mit Hilfe von Suboxid-MBE gewachsen wurden.
Im zweiten Teil dieser Arbeit werden die entwickelten Quellen genutzt und die
BSO und LIO Wachstumsparameter bestimmt, sowie deren Abhängigkeit im Kontext
von thermodynamischen Ellinghamdiagrammen diskutiert. Die Besonderheit
beim BSO Wachstum liegt dabei auf der Verwendung einer Mischquelle bestehend
aus SnO2 + Sn wodurch SnO Suboxid gebildet wird, welches zum Wachstum
beiträgt.
Ein zwei-dimensionalen Elektronengas an der Grenzfläche der BSO/LIO Heterostruktur
wird realisiert durch gezielte Grenzflächenterminierung mit Hilfe einer
Zellverschlusssequenz. Durch die Kontrolle der Grenzflächenterminierung
im Monolagenbereich können Ladungsträgerkonzentrationen im Bereich um 3 -
5 × 1013 cm−2 und Beweglichkeiten μ > 100 cm2/Vs zuverlässig und reproduzierbar
realisiert werden. / The present work investigates the growth of BaSnO3/LaInO3 (BSO/LIO) heterostructures
using plasma-assisted molecular beam epitaxy (PA-MBE). Prior to
the realization of the BSO/LIO heterostructure, ways for stable and reliable growth
of both BSO and LIO layers have to be developed. Therefore, the first part of this
thesis addresses the challenges of suboxide formation and suboxide sources.
The knowledge about suboxides is rather old, however, so far it is barely considered
or used in oxide MBE. Dedicated studies performed in this thesis show
that for suboxide sources such as a mixture of SnO2 and Sn the growth kinetics
simplify compared to an elemental source (e.g., Sn).
The efficiency of mixed sources, that is worked out in this thesis, already
led to the growth of other oxides such as Ga2O3 or SnO using suboxide MBE.
In the second part of this thesis growth parameters for BSO and LIO, using the
developed sources, are determined and their dependence in the context of thermodynamic
Ellingham diagrams is discussed. The growth of BSO is realized by
the use of a mixed source consisting of SnO2 + Sn, which forms SnO suboxide
that is contributed to the growth.
A two-dimensional electron gas at the interface of the BSO/LIO heterostructure
is realized by engineering the interface termination using a controlled cell shutter
sequence. By controlling the interface termination down to mono layer precision,
charge carrier densities in the range of 3 - 5 × 1013 cm−2 and mobilities
μ > 100 cm2/Vs can be achieved reliably and reproducibly.
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