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Portrait of Ivan Maximov. Photo: Kennet Ruona

Ivan Maximov

Associate Professor, Coordinator Exploratory Nanotechnology

Portrait of Ivan Maximov. Photo: Kennet Ruona

Semiconductor Nanoelectronic Devices Based on Ballistic and Quantum Effects

Author

  • Jie Sun

Summary, in English

As current silicon-based microelectronic devices and circuits are approaching

their fundamental limits, the research field of nanoelectronics is emerging

worldwide. With this background, the present thesis focuses on semiconductor

nanoelectronic devices based on ballistic and quantum effects.

<br>

The main material studied was a modulation doped In0.75Ga0.25As/InP semiconductor two-dimensional electron gas grown by metal-organic vapor phase epitaxy.

The thesis covers mainly three types of devices and their twofold integration:

in-plane gate transistors, three-terminal ballistic junctions and quantum

dots. Various advanced nanofabrication tools were used to realize the devices, such as electron beam lithography, focused ion beam lithography and atomic layer deposition. The theories behind the analysis of the experimental data include principles of field effect transistors, the Landauer-Büttiker formalism, the constant interaction model, etc.

The principles of in-plane gate transistors can be explained by a classical

theory. The source, drain, one-dimensional channel and two side gates were

in the same plane; a setup that can be obtained by single step lithography.

The gating efficiency of the two independent gates was voltage-dependent,

which resulted in a simplified circuitry for implementing a logic function. At

room temperature, an SR latch with a signal gain of ∼4 was realized by the

integration of two in-plane gate transistors.

Three-terminal ballistic junctions are nonlinear devices based on ballistic

electron transport. When two terminals are applied with voltages, the third

terminal will output a voltage close to the more negative voltage in the two

inputs, as opposed to a simple average of the two. From numerical calculations,

this ballistic effect persists up to room temperature. Three-terminal

ballistic junctions are so robust that nonlinearity is observable in asymmetric

devices and relatively large devices. They can be fabricated on several

materials by assorted techniques. The junctions find their applications in

analogue frequency mixers, phase detectors and digital SR latches and the

circuits are simpler than conventional designs. The intrinsic speed of the

devices is in the GHz or THz regime by virtue of the ballistic transport. It is believed that as-built junctions have a potential as building blocks in future

nanoelectronics.

Quantum dots are zero-dimensional boxes for electrons with a decent

resemblance to natural atoms. Due to their nanoscale size, numerous interesting

quantum effects can be observed. Gate-defined quantum dots were

fabricated in InGaAs/InP by incorporating a high-k HfO2 (20-30 nm thick,

grown by atomic layer deposition) as the gate dielectric. The gate leakage

was suppressed and the gating efficiency improved. At 300 mK, charge stability

diagrams of single and double quantum dots were measured and studied

in detail. Zeeman splitting in a parallel magnetic field and charge sensing by

nearby quantum point contacts were also investigated. The single and double

quantum dots are expected to be useful in fields including single electron

logic, stochastic resonance, spintronics, quantum computing, etc.

Department/s

  • Solid State Physics

Publishing year

2009

Language

English

Document type

Dissertation

Publisher

Lund University (Media-Tryck)

Topic

  • Condensed Matter Physics

Keywords

  • Semiconductor
  • Quantum Dots
  • Ballistic Transport
  • InGaAs/InP 2DEG
  • Nanoelectronics

Status

Published

Supervisor

  • Hongqi Xu
  • Ivan Maximov

ISBN/ISSN/Other

  • ISBN: 978-91-628-7850-4

Defence date

25 September 2009

Defence time

13:15

Defence place

Lecture hall B, Fysiska Institutionen, Professorsgatan 1, Lund University Faculty of Engineering

Opponent

  • Jonathan Bird (Prof.)