{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:61386"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:61386","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Spin-Bahn-Wechselwirkung in niedrigdimensionalen Al x Ga 1-x N/GaN-Elektronengasen","abstract":"Spin-based electronics or magnetoelectronics (short spintronics) intends to use and control the electron spin in semiconductors for switching purpose. The two possible orientations of the electron spin respective to a defined direction in space make the spin to be an ideal bit for information technology. The crystal structure of nitrides is characterized by a lack of inversion symmetry. The later is important, as it leads to a spin-splitting of the energy spectrum, inducing the intended spin precession. Such an asymmetric potential can also be induced by making use of a heterostructure with an asymmetric potential profile in the quantum well. In this case the advantage is that one can control the asymmetry of the potential by varying an applied gate voltage. By this way, one can control the spin-splitting, an effect also known as Rashba-effect. In contrast to conventional III/V-semiconductors, the spin-orbit coupling arising from the crystal and the one from the macroscopic electric field of the heterostructure are of the same kind, so that they both can be considered as Rashba-like. Therefore, two new definitions will be introduced in this work: crystal Rashba effect and two-dimensional Rashba effect. Because of the large band gap in nitride semiconductors a weaker spin-orbit coupling is expected compared to conventional III/V-semiconductors. On the other side, nitride semiconductors are characterized by high polarisation fields, enhancing the spin-orbit coupling. The answer of the question, if spin-orbit coupling is present in nitrides, and if this one is arising much more from the crystal or from the heterostructure, is the subject of this thesis. In the theoretical part of this work the strength of the two-dimensional spin-orbit coupling (i.e. arising from the heterostructure) was calculated by making use of the k.p-formalism. This calculation stated the strength of spin-orbit coupling in AlGaN/GaN heterostructures. As an estimation of the crystal Rashba effect showed to be very complex, no conclusion about the dominant spin-orbit coupling process could be done. Experimental measurements and the observation of weak antilocalisation demonstrated the presence of spin-orbit coupling in AlGaN/GaN heterostructures. The strength of the spin-orbit coupling parameter was determined by fitting the curves with the ILP-Model. The change of the gate-voltage did not induce any change of the spin orbit coupling parameter, so that crystal Rashba effect could be considered as the dominant one in our structures. Moreover, nodes at high magnetic fields were observed in the Shubnikov-de Haas oscillations, as a possible indication of spin-orbit coupling. However a discrepancy between the spin orbit coupling parameter obtained from the weak antilocalisation measured and the one from the nodes in the SdH-oscillations was stated. Nevertheless, the influcence of Aluminium allow fluctuations in the quantum well potential could also be explaining the observation of such nodes.","abstract_html":"Spin-based electronics or magnetoelectronics (short spintronics) intends to use and control the electron spin in semiconductors for switching purpose. The two possible orientations of the electron spin respective to a defined direction in space make the spin to be an ideal bit for information technology. The crystal structure of nitrides is characterized by a lack of inversion symmetry. The later is important, as it leads to a spin-splitting of the energy spectrum, inducing the intended spin precession. Such an asymmetric potential can also be induced by making use of a heterostructure with an asymmetric potential profile in the quantum well. In this case the advantage is that one can control the asymmetry of the potential by varying an applied gate voltage. By this way, one can control the spin-splitting, an effect also known as Rashba-effect. In contrast to conventional III/V-semiconductors, the spin-orbit coupling arising from the crystal and the one from the macroscopic electric field of the heterostructure are of the same kind, so that they both can be considered as Rashba-like. Therefore, two new definitions will be introduced in this work: crystal Rashba effect and two-dimensional Rashba effect. Because of the large band gap in nitride semiconductors a weaker spin-orbit coupling is expected compared to conventional III/V-semiconductors. On the other side, nitride semiconductors are characterized by high polarisation fields, enhancing the spin-orbit coupling. The answer of the question, if spin-orbit coupling is present in nitrides, and if this one is arising much more from the crystal or from the heterostructure, is the subject of this thesis. In the theoretical part of this work the strength of the two-dimensional spin-orbit coupling (i.e. arising from the heterostructure) was calculated by making use of the k.p-formalism. This calculation stated the strength of spin-orbit coupling in AlGaN/GaN heterostructures. As an estimation of the crystal Rashba effect showed to be very complex, no conclusion about the dominant spin-orbit coupling process could be done. Experimental measurements and the observation of weak antilocalisation demonstrated the presence of spin-orbit coupling in AlGaN/GaN heterostructures. The strength of the spin-orbit coupling parameter was determined by fitting the curves with the ILP-Model. The change of the gate-voltage did not induce any change of the spin orbit coupling parameter, so that crystal Rashba effect could be considered as the dominant one in our structures. Moreover, nodes at high magnetic fields were observed in the Shubnikov-de Haas oscillations, as a possible indication of spin-orbit coupling. However a discrepancy between the spin orbit coupling parameter obtained from the weak antilocalisation measured and the one from the nodes in the SdH-oscillations was stated. Nevertheless, the influcence of Aluminium allow fluctuations in the quantum well potential could also be explaining the observation of such nodes.","abstract_has_math":false,"creators":["Thillosen, Nicolas Henri"],"institution":"Publikationsserver der RWTH Aachen University","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Lüth, Hans"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2006,"date_issued":"2006","date_published":"2006","updated_at":"2026-07-30T19:43:10Z","subjects":["info:eu-repo/classification/ddc/530","Borgruppennitride","Ternäres System","Quanten-Hall-Effekt","Elektron","Spin-Bahn-Wechselwirkung","Physik","Rashba-Effekt","Lokalisierung","Antilokalisierung","Halbleiter-Heterostruktur","Rashba-effect","spin-orbit-coupling","weak localization","weak antilocalization","Schubnikov-de-Haas"],"languages":["ger"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123055%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123055%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123055%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/61386","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Lüth, Hans"]},{"key":"dc:creator","label":"Author","values":["Thillosen, Nicolas Henri"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2006"]},{"key":"dc:publisher","label":"Institution","values":["Publikationsserver der RWTH Aachen University"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-16398"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/530","Borgruppennitride","Ternäres System","Quanten-Hall-Effekt","Elektron","Spin-Bahn-Wechselwirkung","Physik","Rashba-Effekt","Lokalisierung","Antilokalisierung","Halbleiter-Heterostruktur","Rashba-effect","spin-orbit-coupling","weak localization","weak antilocalization","Schubnikov-de-Haas"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["ger"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/61386","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123055%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Spin-based electronics or magnetoelectronics (short spintronics) intends to use and control the electron spin in semiconductors for switching purpose. The two possible orientations of the electron spin respective to a defined direction in space make the spin to be an ideal bit for information technology. The crystal structure of nitrides is characterized by a lack of inversion symmetry. The later is important, as it leads to a spin-splitting of the energy spectrum, inducing the intended spin precession. Such an asymmetric potential can also be induced by making use of a heterostructure with an asymmetric potential profile in the quantum well. In this case the advantage is that one can control the asymmetry of the potential by varying an applied gate voltage. By this way, one can control the spin-splitting, an effect also known as Rashba-effect. In contrast to conventional III/V-semiconductors, the spin-orbit coupling arising from the crystal and the one from the macroscopic electric field of the heterostructure are of the same kind, so that they both can be considered as Rashba-like. Therefore, two new definitions will be introduced in this work: crystal Rashba effect and two-dimensional Rashba effect. Because of the large band gap in nitride semiconductors a weaker spin-orbit coupling is expected compared to conventional III/V-semiconductors. On the other side, nitride semiconductors are characterized by high polarisation fields, enhancing the spin-orbit coupling. The answer of the question, if spin-orbit coupling is present in nitrides, and if this one is arising much more from the crystal or from the heterostructure, is the subject of this thesis. In the theoretical part of this work the strength of the two-dimensional spin-orbit coupling (i.e. arising from the heterostructure) was calculated by making use of the k.p-formalism. This calculation stated the strength of spin-orbit coupling in AlGaN/GaN heterostructures. As an estimation of the crystal Rashba effect showed to be very complex, no conclusion about the dominant spin-orbit coupling process could be done. Experimental measurements and the observation of weak antilocalisation demonstrated the presence of spin-orbit coupling in AlGaN/GaN heterostructures. The strength of the spin-orbit coupling parameter was determined by fitting the curves with the ILP-Model. The change of the gate-voltage did not induce any change of the spin orbit coupling parameter, so that crystal Rashba effect could be considered as the dominant one in our structures. Moreover, nodes at high magnetic fields were observed in the Shubnikov-de Haas oscillations, as a possible indication of spin-orbit coupling. However a discrepancy between the spin orbit coupling parameter obtained from the weak antilocalisation measured and the one from the nodes in the SdH-oscillations was stated. Nevertheless, the influcence of Aluminium allow fluctuations in the quantum well potential could also be explaining the observation of such nodes."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Publikationsserver der RWTH Aachen University III, 146 S. : Ill., graph. Darst. (2006). = Aachen, Techn. Hochsch., Diss., 2006"]},{"key":"dc:title","label":"Title","values":["Spin-Bahn-Wechselwirkung in niedrigdimensionalen Al x Ga 1-x N/GaN-Elektronengasen"]}]}],"canonical_facts":{"dc:contributor":["Lüth, Hans"],"dc:coverage":["DE"],"dc:creator":["Thillosen, Nicolas Henri"],"dc:date":["2006"],"dc:description":["Spin-based electronics or magnetoelectronics (short spintronics) intends to use and control the electron spin in semiconductors for switching purpose. The two possible orientations of the electron spin respective to a defined direction in space make the spin to be an ideal bit for information technology. The crystal structure of nitrides is characterized by a lack of inversion symmetry. The later is important, as it leads to a spin-splitting of the energy spectrum, inducing the intended spin precession. Such an asymmetric potential can also be induced by making use of a heterostructure with an asymmetric potential profile in the quantum well. In this case the advantage is that one can control the asymmetry of the potential by varying an applied gate voltage. By this way, one can control the spin-splitting, an effect also known as Rashba-effect. In contrast to conventional III/V-semiconductors, the spin-orbit coupling arising from the crystal and the one from the macroscopic electric field of the heterostructure are of the same kind, so that they both can be considered as Rashba-like. Therefore, two new definitions will be introduced in this work: crystal Rashba effect and two-dimensional Rashba effect. Because of the large band gap in nitride semiconductors a weaker spin-orbit coupling is expected compared to conventional III/V-semiconductors. On the other side, nitride semiconductors are characterized by high polarisation fields, enhancing the spin-orbit coupling. The answer of the question, if spin-orbit coupling is present in nitrides, and if this one is arising much more from the crystal or from the heterostructure, is the subject of this thesis. In the theoretical part of this work the strength of the two-dimensional spin-orbit coupling (i.e. arising from the heterostructure) was calculated by making use of the k.p-formalism. This calculation stated the strength of spin-orbit coupling in AlGaN/GaN heterostructures. As an estimation of the crystal Rashba effect showed to be very complex, no conclusion about the dominant spin-orbit coupling process could be done. Experimental measurements and the observation of weak antilocalisation demonstrated the presence of spin-orbit coupling in AlGaN/GaN heterostructures. The strength of the spin-orbit coupling parameter was determined by fitting the curves with the ILP-Model. The change of the gate-voltage did not induce any change of the spin orbit coupling parameter, so that crystal Rashba effect could be considered as the dominant one in our structures. Moreover, nodes at high magnetic fields were observed in the Shubnikov-de Haas oscillations, as a possible indication of spin-orbit coupling. However a discrepancy between the spin orbit coupling parameter obtained from the weak antilocalisation measured and the one from the nodes in the SdH-oscillations was stated. Nevertheless, the influcence of Aluminium allow fluctuations in the quantum well potential could also be explaining the observation of such nodes."],"dc:identifier":["https://publications.rwth-aachen.de/record/61386","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123055%22"],"dc:language":["ger"],"dc:publisher":["Publikationsserver der RWTH Aachen University"],"dc:relation":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-16398"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:source":["Aachen : Publikationsserver der RWTH Aachen University III, 146 S. : Ill., graph. Darst. (2006). = Aachen, Techn. Hochsch., Diss., 2006"],"dc:subject":["info:eu-repo/classification/ddc/530","Borgruppennitride","Ternäres System","Quanten-Hall-Effekt","Elektron","Spin-Bahn-Wechselwirkung","Physik","Rashba-Effekt","Lokalisierung","Antilokalisierung","Halbleiter-Heterostruktur","Rashba-effect","spin-orbit-coupling","weak localization","weak antilocalization","Schubnikov-de-Haas"],"dc:title":["Spin-Bahn-Wechselwirkung in niedrigdimensionalen Al x Ga 1-x N/GaN-Elektronengasen"],"dc:type":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-30T19:43:10Z"}