Show simple item record

dc.contributor.authorShiri, Daryoush
dc.date.accessioned2012-10-03 15:21:19 (GMT)
dc.date.available2012-10-03 15:21:19 (GMT)
dc.date.issued2012-10-03T15:21:19Z
dc.date.submitted2012-10
dc.identifier.urihttp://hdl.handle.net/10012/7097
dc.description.abstractNarrow silicon nanowires host a rich set of physical phenomena. Understanding these phenomena will open new opportunities for applications of silicon nanowires in optoelectronic devices and adds more functionality to silicon especially in those realms that bulk silicon may not operate remarkably. Compatibility of silicon nanowires with the mainstream fabrication technology is also advantageous. The main theme of this thesis is finding the possibility of using silicon nanowires in light sources; laser and light emitting diodes. Using Tight Binding (TB) and ab-initio Density Functional Theory (DFT) methods it was shown that axial strain can induce significant changes in the effective mass, density of states and bandgap of silicon nanowires. Generality of the observed effects was proven by investigating nanowires of different crystallography, diameter and material (e.g. germanium nanowires). The observed direct to indirect bandgap conversion suggests that strain is able to modulate the light emission properties of silicon nanowires. To investigate this possibility, spontaneous emission time was formulated using perturbation theory including Longitudinal Optical (LO) and Acoustic (LA) phonons. It was observed that corresponding to bandgap conversion, the spontaneous emission time can be modulated by more than one order of magnitude. This emanates from bandgap conversion and symmetry change of wave function in response to strain. A mechanism for population inversion was proposed in the thesis which is based on the Ensemble Monte Carlo (EMC) study of carrier statistics in direct and indirect conduction sub bands. By calculating all possible electron-phonon scattering mechanisms which may deplete the already populated indirect subband, it was shown that at different temperatures and under different electric fields there is a factor of 10 difference between the population of indirect and direct sub bands. This suggests that population inversion can be achieved by biasing an already strained nanowire in its indirect bandgap state. The light emission is possible then by releasing or inverting the strain direction. A few ideas of implementing this experiment were proposed as a patent application. Furthermore the photo absorption of silicon nanowires was calculated using TB method and the role of diameter, optical anisotropy and strain were investigated on band-edge absorption.en
dc.language.isoenen
dc.publisherUniversity of Waterlooen
dc.subjectSilicon Nanowiresen
dc.subjectElectromechanical responseen
dc.subjectStrainen
dc.subjectelecton-phonon scatteringen
dc.subjectphoto absorptionen
dc.subjectspontaneous emissionen
dc.subjectnanowire lasersen
dc.subjectpopulation inversionen
dc.titleElectronic and Optical Properties of Silicon Nanowires: Theory and Modelingen
dc.typeDoctoral Thesisen
dc.pendingfalseen
dc.subject.programElectrical and Computer Engineeringen
uws-etd.degree.departmentElectrical and Computer Engineeringen
uws-etd.degreeDoctor of Philosophyen
uws.typeOfResourceTexten
uws.peerReviewStatusUnrevieweden
uws.scholarLevelGraduateen


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record


UWSpace

University of Waterloo Library
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
519 888 4883

All items in UWSpace are protected by copyright, with all rights reserved.

DSpace software

Service outages