Carrier momentum relaxation in highly doped polar semiconductors and semiconductor heterostructures

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dc.contributor.advisorFahy, Stephen B.en
dc.contributor.authorHauber, Anna Miriam
dc.contributor.funderScience Foundation Irelanden
dc.date.accessioned2017-01-04T09:43:03Z
dc.date.available2017-01-04T09:43:03Z
dc.date.issued2016
dc.date.submitted2016
dc.description.abstractHighly doped polar semiconductors are essential components of today’s semiconductor industry. Most strikingly, transistors in modern electronic devices are polar semiconductor heterostructures. It is important to thoroughly understand carrier transport in such structures. In doped polar semiconductors, collective excitations of the carriers (plasmons) and the atoms (polar phonons) couple. These coupled collective excitations affect the electrical conductivity, here quantified through the carrier mobility. In scattering events, the carriers and the coupled collective modes transfer momentum between each other. Carrier momentum transferred to polar phonons can be lost to other phonons through anharmonic decay, resulting in a finite carrier mobility. The plasmons do not have a decay mechanism which transfers carrier momentum irretrievably. Hence, carrier-plasmon scattering results in infinite carrier mobility. Momentum relaxation due to either carrier–plasmon scattering or carrier–polar-phonon scattering alone are well understood. However, only this thesis manages to treat momentum relaxation due to both scattering mechanisms on an equal footing, enabling us to properly calculate the mobility limited by carrier–coupled plasmon–polar phonon scattering. We achieved this by solving the coupled Boltzmann equations for the carriers and the collective excitations, focusing on the “drag” term and on the anharmonic decay process of the collective modes. Our approach uses dielectric functions to describe both the carrier-collective mode scattering and the decay of the collective modes. We applied our method to bulk polar semiconductors and heterostructures where various polar dielectrics surround a semiconducting monolayer of MoS2, where taking plasmons into account can increase the mobility by up to a factor 15 for certain parameters. This screening effect is up to 85% higher than if calculated with previous methods. To conclude, our approach provides insight into the momentum relaxation mechanism for carrier–coupled collective mode scattering, and better tools for calculating the screened polar phonon and interface polar phonon limited mobility.en
dc.description.sponsorshipScience Foundation Ireland (SFI Grant 12/IA/1601)en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Version
dc.format.mimetypeapplication/pdfen
dc.identifier.citationHauber, A. M. 2016. Carrier momentum relaxation in highly doped polar semiconductors and semiconductor heterostructures. PhD Thesis, University College Cork.en
dc.identifier.endpage202en
dc.identifier.urihttps://hdl.handle.net/10468/3417
dc.language.isoenen
dc.publisherUniversity College Corken
dc.rights© 2016, Anna Miriam Hauber.en
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/3.0/en
dc.subjectPolar semiconductorsen
dc.subjectMomentum relaxationen
dc.subjectCarrier mobilityen
dc.subjectPlasmonsen
dc.subjectPolar optical phononsen
dc.subjectPhonon dragen
dc.subjectLandau dampingen
dc.subjectTwo-dimensional semiconductorsen
dc.subjectDielectric functionsen
dc.subjectDynamic screeningen
dc.thesis.opt-outfalse
dc.titleCarrier momentum relaxation in highly doped polar semiconductors and semiconductor heterostructuresen
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD (Science)en
ucc.workflow.supervisors.fahy@ucc.ie
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