A tight-binding analysis of the electronic properties of III-nitride semiconductors

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dc.contributor.advisor O'Reilly, Eoin P. en
dc.contributor.author Coughlan, Conor Terence
dc.date.accessioned 2016-06-20T11:44:54Z
dc.date.available 2016-06-20T11:44:54Z
dc.date.issued 2016
dc.date.submitted 2016
dc.identifier.citation Coughlan, C. T. 2016. A tight-binding analysis of the electronic properties of III-nitride semiconductors. PhD Thesis, University College Cork. en
dc.identifier.endpage 117 en
dc.identifier.uri http://hdl.handle.net/10468/2761
dc.description.abstract This thesis divides into two distinct parts, both of which are underpinned by the tight-binding model. The first part covers our implementation of the tight-binding model in conjunction with the Berry phase theory of electronic polarisation to probe the atomistic origins of spontaneous polarisation and piezoelectricity as well as attempting to accurately calculate the values and coefficients associated with these phenomena. We first develop an analytic model for the polarisation of a one-dimensional linear chain of atoms. We compare the zincblende and ideal wurtzite structures in terms of effective charges, spontaneous polarisation and piezoelectric coefficients, within a first nearest neighbour tight-binding model. We further compare these to real wurtzite structures and conclude that accurate quantitative results are beyond the scope of this model but qualitative trends can still be described. The second part of this thesis deals with implementing the tight-binding model to investigate the effect of local alloy fluctuations in bulk AlGaN alloys and InGaN quantum wells. We calculate the band gap evolution of Al1_xGaxN across the full composition range and compare it to experiment as well as fitting bowing parameters to the band gap as well as to the conduction band and valence band edges. We also investigate the wavefunction character of the valence band edge to determine the composition at which the optical polarisation switches in Al1_xGaxN alloys. Finally, we examine electron and hole localisation in InGaN quantum wells. We show how the built-in field localises the carriers along the c-axis and how local alloy fluctuations strongly localise the highest hole states in the c-plane, while the electrons remain delocalised in the c-plane. We show how this localisation affects the charge density overlap and also investigate the effect of well width fluctuations on the localisation of the electrons. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2016, Conor Terence Coughlan. en
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/ en
dc.subject Physics en
dc.subject Piezoelectricity en
dc.subject Berry phase en
dc.subject Electronic polarisation en
dc.subject InGaN quantum wells en
dc.subject III-nitride semiconductors en
dc.subject AlN bandgap bowing en
dc.subject Tight binding en
dc.title A tight-binding analysis of the electronic properties of III-nitride semiconductors en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text available en
dc.check.info No embargo required en
dc.description.version Accepted Version
dc.contributor.funder Science Foundation Ireland en
dc.description.status Not peer reviewed en
dc.internal.school Physics en
dc.check.type No Embargo Required
dc.check.reason No embargo required en
dc.check.opt-out No en
dc.thesis.opt-out false
dc.check.embargoformat Not applicable en
ucc.workflow.supervisor eoin.oreilly@tyndall.ie
dc.internal.conferring Summer 2016 en

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© 2016, Conor Terence Coughlan. Except where otherwise noted, this item's license is described as © 2016, Conor Terence Coughlan.
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