Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 263171
Loughborough University

Loughborough University Institutional Repository

Please use this identifier to cite or link to this item: https://dspace.lboro.ac.uk/2134/17158

Title: Charge dynamics in coupled semiconductor superlattices
Authors: Matharu, Satpal
Keywords: Semiconductor
Issue Date: 2015
Publisher: © S. Matharu
Abstract: In this thesis, we investigate the collective electron dynamics in single and coupled superlattice systems under the influence of a DC electric field. Firstly, we illustrate that Bloch oscillations suppress electron transport and the resulting charge domains form self-sustained current oscillations. Upon the application of a tilted magnetic field, stochastic web structures are shown to form in the phase space of the electron trajectory. This occurs only when the Bloch and cyclotron frequencies are commensurate allowing the electrons to demonstrate chaotic unbounded trajectories, leading to an increase in transport. The charge domain dynamics also present additional peaks during such resonances. The rapid changes in the dynamical states found is an example of non-KAM chaos. We show then the amplitude and frequency of current oscillations in a single superlattice can be controlled. Secondly, two models are designed to mutually couple two semiconductor superlattices by a common resistive load. We examine the effects of coupling strength and frequency detuning on the collective current dynamics. The devices are considered to be arranged together on a single substrate as well as on individual substrates. Large AC power is witnessed during anti-phase and in-phase synchronization between current oscillations. Finally, two superlattices are coupled through a resonance circuit incorporating single mode resonances from external influences in the circuit. In this system, chaotic current dynamics are induced with regions of chaos separating different regions of synchronization. High frequency oscillations with minimal phase difference cause the largest power generation. In all three coupling models high frequency components are found in the Fourier power spectra. The power generated in the coupled systems is found greater and at times more than double the power generated in the autonomous superlattice. Thus this thesis provides innovative methods of enhancing and controlling powerful high-frequency signals. This effectively gives manipulation over the intensity of the electromagnetic radiation produced by the superlattice.
Description: A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.
Sponsor: Loughborough University
URI: https://dspace.lboro.ac.uk/2134/17158
Appears in Collections:PhD Theses (Physics)

Files associated with this item:

File Description SizeFormat
Thesis-2015-Matharu.pdf6.73 MBAdobe PDFView/Open
Form-2015-Matharu.pdf893.49 kBAdobe PDFView/Open


SFX Query

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.