{"id":{"repo_id":"udel","oai_identifier":"oai:udspace.udel.edu:19716/24152"},"canonical_url":"https://search.dev.ndltd.org/etd/udel/oai:udspace.udel.edu:19716/24152","repository":{"repo_id":"udel","name":"University of Delaware","base_url":"https://udspace.udel.edu/server/oai/request"},"display":{"title":"Exploring single hole states in InAs/GaAs quantum dots and quantum dot molecules under 2-D electric fields","abstract":"InAs/GaAs quantum dots (QDs) and quantum dot molecules (QDMs) are self-assembled semiconductor nanostructures that can trap a single electron or hole in a 3-D potential-well. Grown by molecular beam epitaxy (MBE), they have excellent optical qualities that can be used in applications for quantum information processing and quantum computing. Specifically, hole spins in a single QD/QDM have longer decoherence time than electron spins due to the lack of hyperfine interaction, making hole spins a great qubit candidate. However, many challenges such as QD growth, device integration, and spin manipulation inhibit the scalability of a hole-spin-based quantum information platform. A deeper understanding of the hole spin physics and the QD/QDM material system is needed to advance device engineering opportunities. ☐ In this dissertation work, we explore a hole spin in an InAs/GaAs QD/QDM under a 2-D electric field. We develop a hybrid computational method that combines a tight-binding atomistic simulation and a finite matrix approximation. This hybrid method can quickly explore the properties of a single hole spin state under a variety of electric field conditions. We discover that a hole spin in a single QD can be polarized in the vertical direction with an in-plane (lateral) electric field and a Voigt (lateral) direction magnetic field. We show that this effect persists with different QD shape, composition, and orientation. We also demonstrate the ability to control hole spin states using a lateral electric field in a QDM, particularly the ability to induce hole spin mixing with a gradient 2-D electric field. We will discuss the spin texture concept that explains these exotic spin effects using an animated visualization algorithm. ☐ We also present the experimental effort to apply 2-D electric field to a single QD/QDM. We use COMSOL semiconductor simulation to design a 3-electrode device that can apply 2-D electric field in GaAs. We discuss a range of device parameters and their influence on the device performance. We grow a single QD sample in an intrinsic GaAs matrix using MBE. We fabricate the 3-electrode device on this sample using electron beam lithography, ICP etching, Ion Milling and angled e-beam metal evaporation. The device is then characterized by low-temperature micro-photoluminescence. We show that we are able to control the charging of a single hole state in a QD using two different voltage geometries. Combining the experimental data with the COMSOL simulation results, we show the charging comes from the induced 2-D electric field around a single QD. We will discuss the improvements required to continue on the path to full 2-D field control of a single QD.","abstract_html":"InAs/GaAs quantum dots (QDs) and quantum dot molecules (QDMs) are self-assembled semiconductor nanostructures that can trap a single electron or hole in a 3-D potential-well. Grown by molecular beam epitaxy (MBE), they have excellent optical qualities that can be used in applications for quantum information processing and quantum computing. Specifically, hole spins in a single QD/QDM have longer decoherence time than electron spins due to the lack of hyperfine interaction, making hole spins a great qubit candidate. However, many challenges such as QD growth, device integration, and spin manipulation inhibit the scalability of a hole-spin-based quantum information platform. A deeper understanding of the hole spin physics and the QD/QDM material system is needed to advance device engineering opportunities. ☐ In this dissertation work, we explore a hole spin in an InAs/GaAs QD/QDM under a 2-D electric field. We develop a hybrid computational method that combines a tight-binding atomistic simulation and a finite matrix approximation. This hybrid method can quickly explore the properties of a single hole spin state under a variety of electric field conditions. We discover that a hole spin in a single QD can be polarized in the vertical direction with an in-plane (lateral) electric field and a Voigt (lateral) direction magnetic field. We show that this effect persists with different QD shape, composition, and orientation. We also demonstrate the ability to control hole spin states using a lateral electric field in a QDM, particularly the ability to induce hole spin mixing with a gradient 2-D electric field. We will discuss the spin texture concept that explains these exotic spin effects using an animated visualization algorithm. ☐ We also present the experimental effort to apply 2-D electric field to a single QD/QDM. We use COMSOL semiconductor simulation to design a 3-electrode device that can apply 2-D electric field in GaAs. We discuss a range of device parameters and their influence on the device performance. We grow a single QD sample in an intrinsic GaAs matrix using MBE. We fabricate the 3-electrode device on this sample using electron beam lithography, ICP etching, Ion Milling and angled e-beam metal evaporation. The device is then characterized by low-temperature micro-photoluminescence. We show that we are able to control the charging of a single hole state in a QD using two different voltage geometries. Combining the experimental data with the COMSOL simulation results, we show the charging comes from the induced 2-D electric field around a single QD. We will discuss the improvements required to continue on the path to full 2-D field control of a single QD.","abstract_has_math":false,"creators":["Ma, Xiangyu"],"institution":"University of Delaware","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018","date_published":"2018","updated_at":"2026-07-24T05:11:20Z","subjects":[],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.58088/k7s8-6y56"],"render_values":[{"text":"https://doi.org/10.58088/k7s8-6y56","href":"https://doi.org/10.58088/k7s8-6y56","code":true}]}]},"links":{"outbound_url":"http://udspace.udel.edu/handle/19716/24152","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Ma, Xiangyu"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2019-05-14T11:56:27Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2019-05-14T11:56:27Z"]},{"key":"dc:date.issued","label":"Date","values":["2018"]},{"key":"dc:publisher","label":"Institution","values":["University of Delaware"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.58088/k7s8-6y56"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://udspace.udel.edu/handle/19716/24152"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["InAs/GaAs quantum dots (QDs) and quantum dot molecules (QDMs) are self-assembled semiconductor nanostructures that can trap a single electron or hole in a 3-D potential-well. Grown by molecular beam epitaxy (MBE), they have excellent optical qualities that can be used in applications for quantum information processing and quantum computing. Specifically, hole spins in a single QD/QDM have longer decoherence time than electron spins due to the lack of hyperfine interaction, making hole spins a great qubit candidate. However, many challenges such as QD growth, device integration, and spin manipulation inhibit the scalability of a hole-spin-based quantum information platform. A deeper understanding of the hole spin physics and the QD/QDM material system is needed to advance device engineering opportunities. ☐ In this dissertation work, we explore a hole spin in an InAs/GaAs QD/QDM under a 2-D electric field. We develop a hybrid computational method that combines a tight-binding atomistic simulation and a finite matrix approximation. This hybrid method can quickly explore the properties of a single hole spin state under a variety of electric field conditions. We discover that a hole spin in a single QD can be polarized in the vertical direction with an in-plane (lateral) electric field and a Voigt (lateral) direction magnetic field. We show that this effect persists with different QD shape, composition, and orientation. We also demonstrate the ability to control hole spin states using a lateral electric field in a QDM, particularly the ability to induce hole spin mixing with a gradient 2-D electric field. We will discuss the spin texture concept that explains these exotic spin effects using an animated visualization algorithm. ☐ We also present the experimental effort to apply 2-D electric field to a single QD/QDM. We use COMSOL semiconductor simulation to design a 3-electrode device that can apply 2-D electric field in GaAs. We discuss a range of device parameters and their influence on the device performance. We grow a single QD sample in an intrinsic GaAs matrix using MBE. We fabricate the 3-electrode device on this sample using electron beam lithography, ICP etching, Ion Milling and angled e-beam metal evaporation. The device is then characterized by low-temperature micro-photoluminescence. We show that we are able to control the charging of a single hole state in a QD using two different voltage geometries. Combining the experimental data with the COMSOL simulation results, we show the charging comes from the induced 2-D electric field around a single QD. We will discuss the improvements required to continue on the path to full 2-D field control of a single QD."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Exploring single hole states in InAs/GaAs quantum dots and quantum dot molecules under 2-D electric fields"]}]}],"canonical_facts":{"dc:creator":["Ma, Xiangyu"],"dc:date.accessioned":["2019-05-14T11:56:27Z"],"dc:date.available":["2019-05-14T11:56:27Z"],"dc:date.issued":["2018"],"dc:description.abstract":["InAs/GaAs quantum dots (QDs) and quantum dot molecules (QDMs) are self-assembled semiconductor nanostructures that can trap a single electron or hole in a 3-D potential-well. Grown by molecular beam epitaxy (MBE), they have excellent optical qualities that can be used in applications for quantum information processing and quantum computing. Specifically, hole spins in a single QD/QDM have longer decoherence time than electron spins due to the lack of hyperfine interaction, making hole spins a great qubit candidate. However, many challenges such as QD growth, device integration, and spin manipulation inhibit the scalability of a hole-spin-based quantum information platform. A deeper understanding of the hole spin physics and the QD/QDM material system is needed to advance device engineering opportunities. ☐ In this dissertation work, we explore a hole spin in an InAs/GaAs QD/QDM under a 2-D electric field. We develop a hybrid computational method that combines a tight-binding atomistic simulation and a finite matrix approximation. This hybrid method can quickly explore the properties of a single hole spin state under a variety of electric field conditions. We discover that a hole spin in a single QD can be polarized in the vertical direction with an in-plane (lateral) electric field and a Voigt (lateral) direction magnetic field. We show that this effect persists with different QD shape, composition, and orientation. We also demonstrate the ability to control hole spin states using a lateral electric field in a QDM, particularly the ability to induce hole spin mixing with a gradient 2-D electric field. We will discuss the spin texture concept that explains these exotic spin effects using an animated visualization algorithm. ☐ We also present the experimental effort to apply 2-D electric field to a single QD/QDM. We use COMSOL semiconductor simulation to design a 3-electrode device that can apply 2-D electric field in GaAs. We discuss a range of device parameters and their influence on the device performance. We grow a single QD sample in an intrinsic GaAs matrix using MBE. We fabricate the 3-electrode device on this sample using electron beam lithography, ICP etching, Ion Milling and angled e-beam metal evaporation. The device is then characterized by low-temperature micro-photoluminescence. We show that we are able to control the charging of a single hole state in a QD using two different voltage geometries. Combining the experimental data with the COMSOL simulation results, we show the charging comes from the induced 2-D electric field around a single QD. We will discuss the improvements required to continue on the path to full 2-D field control of a single QD."],"dc:description.degree":["Ph.D."],"dc:identifier.doi":["https://doi.org/10.58088/k7s8-6y56"],"dc:identifier.uri":["http://udspace.udel.edu/handle/19716/24152"],"dc:publisher":["University of Delaware"],"dc:title":["Exploring single hole states in InAs/GaAs quantum dots and quantum dot molecules under 2-D electric fields"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T05:11:20Z"}