{"id":{"repo_id":"ohiolink","oai_identifier":"oai:etd.ohiolink.edu:osu1366229216"},"canonical_url":"https://search.dev.ndltd.org/etd/ohiolink/oai:etd.ohiolink.edu:osu1366229216","repository":{"repo_id":"ohiolink","name":"OhioLINK","base_url":"https://etd.ohiolink.edu/acprod/odb_etd/ws/oai/oai"},"display":{"title":"Interface Trap Characterization of ALD-grown Al2O3/GaN MIS Capacitors","abstract":"The use of Al2O3 deposited by atomic layer deposition (ALD) in GaN-based transistors may improve device performance, by reducing gate leakage and passivating surface states, and is receiving great interest. However, little work has been done to characterize interface states and bulk dielectric defects in such structures. The presence, concentration and distribution of defects likely depend on interface nucleation and the ALD process. Thus, process optimization will require identifying traps and fixed charges, determining location within the layers and improving fabrication to decrease trap and fixed charge densities. This work centers on characterizing traps at the interface between GaN and ALD-grown Al2O3. Interface defect characterization is performed by constant capacitance deep level transient spectroscopy (CC-DLTS) in tandem with constant capacitance deep level optical spectroscopy (CC-DLOS), making it possible to probe the interface over the entire GaN bandgap. To investigate the role of Al2O3 thickness on interface state densities and explore the presence of Al2O3 bulk traps, 6.8, 13.4, and 19.8nm thick films of ALD Al2O3 were deposited on NH3-MBE n-type Ga-polar GaN substrates. The as-deposited Al2O3 films were fabricated into MIS capacitors using e-beam evaporated semitransparent Ni contacts on the Al2O3 and Ti/Al/Ni/Au Ohmic contacts to the GaN. Additionally, Ni/GaN Schottky diodes were fabricated on the substrate to separately determine bulk traps in the GaN.Using CC-DLTS/DLOS, the interface trap densities, Dit, of the three films were determined to be nearly identical, independent of Al2O3 thickness. Such agreement suggests that the concentration of traps within the oxide is small compared to the density of traps at the interface. Bulk GaN traps are accounted for in the analysis of the MIS spectroscopy signals. The Al2O3/GaN Dit spectra had a U-shape with Dit ~1012cm-2eV-1 near the conduction band edge, ~1011cm-2eV-1 mid-gap, and ~1014cm-2eV-1 near the valence band edge. The 6.8nm and 13.4nm Al2O3 samples showed a factor of four and a factor of two increase in Dit near the conduction band edge, respectively, compared with the 19.8nm Al2O3 sample. The inverse relationship with thickness indicates this increase cannot be due to bulk Al2O3 traps and indicates that the interface is slightly improved with increased film thickness. These films were not annealed, so the increased time at 300°C during the deposition may lead to slight reduction in Dit.","abstract_html":"The use of Al<sub>2</sub>O<sub>3</sub> deposited by atomic layer deposition (ALD) in GaN-based transistors may improve device performance, by reducing gate leakage and passivating surface states, and is receiving great interest. However, little work has been done to characterize interface states and bulk dielectric defects in such structures. The presence, concentration and distribution of defects likely depend on interface nucleation and the ALD process. Thus, process optimization will require identifying traps and fixed charges, determining location within the layers and improving fabrication to decrease trap and fixed charge densities. This work centers on characterizing traps at the interface between GaN and ALD-grown Al<sub>2</sub>O<sub>3</sub>. Interface defect characterization is performed by constant capacitance deep level transient spectroscopy (CC-DLTS) in tandem with constant capacitance deep level optical spectroscopy (CC-DLOS), making it possible to probe the interface over the entire GaN bandgap. To investigate the role of Al<sub>2</sub>O<sub>3</sub> thickness on interface state densities and explore the presence of Al<sub>2</sub>O<sub>3</sub> bulk traps, 6.8, 13.4, and 19.8nm thick films of ALD Al<sub>2</sub>O<sub>3</sub> were deposited on NH<sub>3</sub>-MBE n-type Ga-polar GaN substrates. The as-deposited Al<sub>2</sub>O<sub>3</sub> films were fabricated into MIS capacitors using e-beam evaporated semitransparent Ni contacts on the Al<sub>2</sub>O<sub>3</sub> and Ti/Al/Ni/Au Ohmic contacts to the GaN. Additionally, Ni/GaN Schottky diodes were fabricated on the substrate to separately determine bulk traps in the GaN.Using CC-DLTS/DLOS, the interface trap densities, D<sub>it</sub>, of the three films were determined to be nearly identical, independent of Al<sub>2</sub>O<sub>3</sub> thickness. Such agreement suggests that the concentration of traps within the oxide is small compared to the density of traps at the interface. Bulk GaN traps are accounted for in the analysis of the MIS spectroscopy signals. The Al<sub>2</sub>O<sub>3</sub>/GaN D<sub>it</sub> spectra had a U-shape with D<sub>it</sub> ~10<sup>12</sup>cm<sup>-2</sup>eV<sup>-1</sup> near the conduction band edge, ~10<sup>11</sup>cm<sup>-2</sup>eV<sup>-1</sup> mid-gap, and ~10<sup>14</sup>cm<sup>-2</sup>eV<sup>-1</sup> near the valence band edge. The 6.8nm and 13.4nm Al<sub>2</sub>O<sub>3</sub> samples showed a factor of four and a factor of two increase in D<sub>it</sub> near the conduction band edge, respectively, compared with the 19.8nm Al<sub>2</sub>O<sub>3</sub> sample. The inverse relationship with thickness indicates this increase cannot be due to bulk Al<sub>2</sub>O<sub>3</sub> traps and indicates that the interface is slightly improved with increased film thickness. These films were not annealed, so the increased time at 300°C during the deposition may lead to slight reduction in D<sub>it</sub>.","abstract_has_math":false,"creators":["Jackson, Christine M."],"institution":"The Ohio State University","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Electrical and Computer Engineering","degree_department":null,"school":null,"contributors":["Ringel, Steven"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013-07-25","date_published":"2013-07-25","updated_at":"2026-07-24T03:37:46Z","subjects":["Electrical Engineering"],"languages":["English"],"rights":["unrestricted","This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://rave.ohiolink.edu/etdc/view?acc_num=osu1366229216","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Ringel, Steven"]},{"key":"dc:creator","label":"Author","values":["Jackson, Christine M."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2013-07-25"]},{"key":"dc:publisher","label":"Institution","values":["The Ohio State University / OhioLINK"]},{"key":"dc:type","label":"Dc Type","values":["Electronic Thesis or Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical and Computer Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["The Ohio State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Electrical Engineering"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]},{"key":"dc:rights","label":"Dc Rights","values":["unrestricted","This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://rave.ohiolink.edu/etdc/view?acc_num=osu1366229216"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The use of Al2O3 deposited by atomic layer deposition (ALD) in GaN-based transistors may improve device performance, by reducing gate leakage and passivating surface states, and is receiving great interest. However, little work has been done to characterize interface states and bulk dielectric defects in such structures. The presence, concentration and distribution of defects likely depend on interface nucleation and the ALD process. Thus, process optimization will require identifying traps and fixed charges, determining location within the layers and improving fabrication to decrease trap and fixed charge densities. This work centers on characterizing traps at the interface between GaN and ALD-grown Al2O3. Interface defect characterization is performed by constant capacitance deep level transient spectroscopy (CC-DLTS) in tandem with constant capacitance deep level optical spectroscopy (CC-DLOS), making it possible to probe the interface over the entire GaN bandgap. To investigate the role of Al2O3 thickness on interface state densities and explore the presence of Al2O3 bulk traps, 6.8, 13.4, and 19.8nm thick films of ALD Al2O3 were deposited on NH3-MBE n-type Ga-polar GaN substrates. The as-deposited Al2O3 films were fabricated into MIS capacitors using e-beam evaporated semitransparent Ni contacts on the Al2O3 and Ti/Al/Ni/Au Ohmic contacts to the GaN. Additionally, Ni/GaN Schottky diodes were fabricated on the substrate to separately determine bulk traps in the GaN.Using CC-DLTS/DLOS, the interface trap densities, Dit, of the three films were determined to be nearly identical, independent of Al2O3 thickness. Such agreement suggests that the concentration of traps within the oxide is small compared to the density of traps at the interface. Bulk GaN traps are accounted for in the analysis of the MIS spectroscopy signals. The Al2O3/GaN Dit spectra had a U-shape with Dit ~1012cm-2eV-1 near the conduction band edge, ~1011cm-2eV-1 mid-gap, and ~1014cm-2eV-1 near the valence band edge. The 6.8nm and 13.4nm Al2O3 samples showed a factor of four and a factor of two increase in Dit near the conduction band edge, respectively, compared with the 19.8nm Al2O3 sample. The inverse relationship with thickness indicates this increase cannot be due to bulk Al2O3 traps and indicates that the interface is slightly improved with increased film thickness. These films were not annealed, so the increased time at 300°C during the deposition may lead to slight reduction in Dit."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf","921.4 KB"]},{"key":"dc:title","label":"Title","values":["Interface Trap Characterization of ALD-grown Al2O3/GaN MIS Capacitors"]}]}],"canonical_facts":{"dc:contributor":["Ringel, Steven"],"dc:creator":["Jackson, Christine M."],"dc:date":["2013-07-25"],"dc:description":["The use of Al2O3 deposited by atomic layer deposition (ALD) in GaN-based transistors may improve device performance, by reducing gate leakage and passivating surface states, and is receiving great interest. However, little work has been done to characterize interface states and bulk dielectric defects in such structures. The presence, concentration and distribution of defects likely depend on interface nucleation and the ALD process. Thus, process optimization will require identifying traps and fixed charges, determining location within the layers and improving fabrication to decrease trap and fixed charge densities. This work centers on characterizing traps at the interface between GaN and ALD-grown Al2O3. Interface defect characterization is performed by constant capacitance deep level transient spectroscopy (CC-DLTS) in tandem with constant capacitance deep level optical spectroscopy (CC-DLOS), making it possible to probe the interface over the entire GaN bandgap. To investigate the role of Al2O3 thickness on interface state densities and explore the presence of Al2O3 bulk traps, 6.8, 13.4, and 19.8nm thick films of ALD Al2O3 were deposited on NH3-MBE n-type Ga-polar GaN substrates. The as-deposited Al2O3 films were fabricated into MIS capacitors using e-beam evaporated semitransparent Ni contacts on the Al2O3 and Ti/Al/Ni/Au Ohmic contacts to the GaN. Additionally, Ni/GaN Schottky diodes were fabricated on the substrate to separately determine bulk traps in the GaN.Using CC-DLTS/DLOS, the interface trap densities, Dit, of the three films were determined to be nearly identical, independent of Al2O3 thickness. Such agreement suggests that the concentration of traps within the oxide is small compared to the density of traps at the interface. Bulk GaN traps are accounted for in the analysis of the MIS spectroscopy signals. The Al2O3/GaN Dit spectra had a U-shape with Dit ~1012cm-2eV-1 near the conduction band edge, ~1011cm-2eV-1 mid-gap, and ~1014cm-2eV-1 near the valence band edge. The 6.8nm and 13.4nm Al2O3 samples showed a factor of four and a factor of two increase in Dit near the conduction band edge, respectively, compared with the 19.8nm Al2O3 sample. The inverse relationship with thickness indicates this increase cannot be due to bulk Al2O3 traps and indicates that the interface is slightly improved with increased film thickness. These films were not annealed, so the increased time at 300°C during the deposition may lead to slight reduction in Dit."],"dc:format":["application/pdf","921.4 KB"],"dc:identifier":["http://rave.ohiolink.edu/etdc/view?acc_num=osu1366229216"],"dc:language":["English"],"dc:publisher":["The Ohio State University / OhioLINK"],"dc:rights":["unrestricted","This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws."],"dc:subject":["Electrical Engineering"],"dc:title":["Interface Trap Characterization of ALD-grown Al2O3/GaN MIS Capacitors"],"dc:type":["Electronic Thesis or Dissertation"],"thesis:degree_discipline":["Electrical and Computer Engineering"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["The Ohio State University"]},"updated_at":"2026-07-24T03:37:46Z"}