ZnO based photo-thin-film-transistors with actively tunable photoresponse in the visible spectrum

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buir.advisorOkyay, Ali Kemal
dc.contributor.authorAygün, Levent Erdal
dc.date.accessioned2016-01-08T20:02:45Z
dc.date.available2016-01-08T20:02:45Z
dc.date.issued2013
dc.descriptionAnkara : The Department of Electrical and Electronics Engineering and the Graduate School of Engineering and Science of Bilkent University, 2013.en_US
dc.descriptionThesis (Master's) -- Bilkent University, 2013.en_US
dc.descriptionIncludes bibliographical references leaves 51-56.en_US
dc.description.abstractZinc oxide, ZnO, is an important material for wide range of optoelectronic device applications. Especially, ZnO is famous with its large exciton binding energy of 60 meV which makes it a good candidate for ultraviolet light emitting diodes and lasers. Moreover, its high carrier mobility and wide band gap of 3.37 eV (368 nm) makes it a promising material for transparent electronics and UV photodetectors. However, ZnO has crystallographic defect states (e.g. oxygen vacancies, zinc interstitials) which degrade the performance of ZnO based LEDs, lasers and UV photodiodes. In this thesis, ZnO based photo-thin-film-transistors (photo-TFTs) with visible light response by using their defect states to absorb subbandgap photons are investigated. The design, fabrication and characterization of ZnO based photoTFTs are presented. A photo-TFT is a three-terminal optoelectronic device that is a photoconductor structure with an additional gate terminal which actively tunes electrical and optical properties of photoconductive material. In a clean room environment, ZnO based photo-TFTs with various device sizes are fabricated at different ZnO channel layer deposition temperatures (ranging from 80 to 250 °C). Initially, TFT characteristics of fabricated devices are characterized to show that the gate terminal dynamically modulates ZnO’s channel conductivity. Moreover, the effects of the device size and the deposition temperature on device performance are investigated. Then, the optical characterization of ZnO film deposited at 250° C is conducted via absorption and photoluminescence measurements in order to investigate its visible light absorption characteristics and the energy levels of its defect states in the forbidden band gap of ZnO. After that, the responsivity measurements are reported from ZnO based photo-TFTs fabricated at 250 °C and the active tuning mechanism of visible light photoresponse is discussed. Finally, the effects of the deposition temperature and the device size on the visible light responsivity are presented.en_US
dc.description.provenanceMade available in DSpace on 2016-01-08T20:02:45Z (GMT). No. of bitstreams: 1 0006755.pdf: 2748358 bytes, checksum: 0b57e0d92daf87e376b59603d4252afe (MD5)en
dc.description.statementofresponsibilityAygün, Levent Erdalen_US
dc.format.extentxvi, 56 leaves, illustrations, tables, graphsen_US
dc.identifier.urihttp://hdl.handle.net/11693/16898
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectZnOen_US
dc.subjectTFTen_US
dc.subjectphotoconductoren_US
dc.subjectphoto-TFTen_US
dc.subjectphotodetectoren_US
dc.subject.lccTK7871.96.T45 A94 2013en_US
dc.subject.lcshThin film transistors.en_US
dc.subject.lcshThin films.en_US
dc.subject.lcshZinc oxide.en_US
dc.subject.lcshPhoton detectors.en_US
dc.titleZnO based photo-thin-film-transistors with actively tunable photoresponse in the visible spectrumen_US
dc.typeThesisen_US
thesis.degree.disciplineElectrical and Electronic Engineering
thesis.degree.grantorBilkent University
thesis.degree.levelMaster's
thesis.degree.nameMS (Master of Science)

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