{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/107848"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/107848","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Atomic layer deposition Al2O3-passivated AlGaN/GaN high-electron-mobility transistors on Si(111) towards reliable high-speed electronics","abstract":"(Al)GaN-based transistors are the backbones of next-generation high power/frequency electronics. However, various challenges with this exciting technology still necessitate more comprehensive investigations. In particular, epitaxially growing high-quality (Al)GaN layers on foreign substrates, forming low-resistance ohmic contacts on (Al)GaN materials, properly passivating (Al)GaN surfaces, and reducing leakage currents are of great importance. In this dissertation, these challenges are individually addressed along with respective detailed studies. It is shown that a low GaN in-plane tensile strain allows a higher 2D electron gas mobility due to the alleviated interface roughness scattering. In addition, an ohmic contact specific resistance of 4 × 10-6 Ω–cm2 with Ti/Al/Ni/Au metal stacks has been achieved by three-step rapid thermal annealing. Furthermore, it is revealed that annealed, thin-Al2O3 dielectric is an effective (Al)GaN surface passivation alternative for minimizing passivation-associated parasitic capacitance, yet non-ideal for significantly suppressing gate leakage current in metal-insulator-semiconductor structures due to the governing trap-assisted tunneling carrier transport mechanism. A 3.5 µm Schottky-gate AlGaN/GaN HEMT with VT and gm of -0.87 V and 131.67 mS/mm, respectively, at VDS = 3.5 V has been demonstrated. The measured high Schottky gate leakage current and OFF-state drain current are believed to be responsible for the large subthreshold swing and low drain current on/off ratio. A passivation-last process followed by post-metallization annealing is then utilized, which largely reduces the reverse biased Schottky-gate leakage current and OFF-state drain current, leading to a low subthreshold swing of 84.75 mV/dec and a high drain current on/off ratio of 2.1 × 107. Together, the presented results add constructive inputs to the realization of reliable AlGaN/GaN HEMTs on Si(111) towards reliable high-speed electronics.","abstract_html":"(Al)GaN-based transistors are the backbones of next-generation high power/frequency electronics. However, various challenges with this exciting technology still necessitate more comprehensive investigations. In particular, epitaxially growing high-quality (Al)GaN layers on foreign substrates, forming low-resistance ohmic contacts on (Al)GaN materials, properly passivating (Al)GaN surfaces, and reducing leakage currents are of great importance. In this dissertation, these challenges are individually addressed along with respective detailed studies. It is shown that a low GaN in-plane tensile strain allows a higher 2D electron gas mobility due to the alleviated interface roughness scattering. In addition, an ohmic contact specific resistance of 4 × 10-6 Ω–cm2 with Ti/Al/Ni/Au metal stacks has been achieved by three-step rapid thermal annealing. Furthermore, it is revealed that annealed, thin-Al2O3 dielectric is an effective (Al)GaN surface passivation alternative for minimizing passivation-associated parasitic capacitance, yet non-ideal for significantly suppressing gate leakage current in metal-insulator-semiconductor structures due to the governing trap-assisted tunneling carrier transport mechanism. A 3.5 µm Schottky-gate AlGaN/GaN HEMT with VT and gm of -0.87 V and 131.67 mS/mm, respectively, at VDS = 3.5 V has been demonstrated. The measured high Schottky gate leakage current and OFF-state drain current are believed to be responsible for the large subthreshold swing and low drain current on/off ratio. A passivation-last process followed by post-metallization annealing is then utilized, which largely reduces the reverse biased Schottky-gate leakage current and OFF-state drain current, leading to a low subthreshold swing of 84.75 mV/dec and a high drain current on/off ratio of 2.1 × 107. Together, the presented results add constructive inputs to the realization of reliable AlGaN/GaN HEMTs on Si(111) towards reliable high-speed electronics.","abstract_has_math":false,"creators":["Lee, Hsuan-Ping"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Electrical & Computer Engr","degree_department":null,"school":null,"contributors":["Bayram, Can","Kim, Kyekyoon","Leburton, Jean-Pierre","Rosenbaum, Elyse"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2020,"date_issued":"2020-08-26T21:53:56Z","date_published":"2020-08-26T21:53:56Z","updated_at":"2026-07-22T22:24:47Z","subjects":["AlGaN/GaN HEMT, Si(111), high-speed electronics"],"languages":["en"],"rights":["© 2020 Hsuan-Ping Lee"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/107848","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Bayram, Can","Kim, Kyekyoon","Leburton, Jean-Pierre","Rosenbaum, Elyse"]},{"key":"dc:creator","label":"Author","values":["Lee, Hsuan-Ping"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2020-08-26T21:53:56Z","2020-01-31","2020-05"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical & Computer Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["AlGaN/GaN HEMT, Si(111), high-speed electronics"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["© 2020 Hsuan-Ping Lee"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/107848"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["(Al)GaN-based transistors are the backbones of next-generation high power/frequency electronics. However, various challenges with this exciting technology still necessitate more comprehensive investigations. In particular, epitaxially growing high-quality (Al)GaN layers on foreign substrates, forming low-resistance ohmic contacts on (Al)GaN materials, properly passivating (Al)GaN surfaces, and reducing leakage currents are of great importance. In this dissertation, these challenges are individually addressed along with respective detailed studies. It is shown that a low GaN in-plane tensile strain allows a higher 2D electron gas mobility due to the alleviated interface roughness scattering. In addition, an ohmic contact specific resistance of 4 × 10-6 Ω–cm2 with Ti/Al/Ni/Au metal stacks has been achieved by three-step rapid thermal annealing. Furthermore, it is revealed that annealed, thin-Al2O3 dielectric is an effective (Al)GaN surface passivation alternative for minimizing passivation-associated parasitic capacitance, yet non-ideal for significantly suppressing gate leakage current in metal-insulator-semiconductor structures due to the governing trap-assisted tunneling carrier transport mechanism. A 3.5 µm Schottky-gate AlGaN/GaN HEMT with VT and gm of -0.87 V and 131.67 mS/mm, respectively, at VDS = 3.5 V has been demonstrated. The measured high Schottky gate leakage current and OFF-state drain current are believed to be responsible for the large subthreshold swing and low drain current on/off ratio. A passivation-last process followed by post-metallization annealing is then utilized, which largely reduces the reverse biased Schottky-gate leakage current and OFF-state drain current, leading to a low subthreshold swing of 84.75 mV/dec and a high drain current on/off ratio of 2.1 × 107. Together, the presented results add constructive inputs to the realization of reliable AlGaN/GaN HEMTs on Si(111) towards reliable high-speed electronics.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2020-08-25 without embargo terms","The student, Hsuan-Ping Lee, accepted the attached license on 2020-01-29 at 15:47.","The student, Hsuan-Ping Lee, submitted this Dissertation for approval on 2020-01-29 at 15:50.","This Dissertation was approved for publication on 2020-01-31 at 10:09.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14860 on 2020-08-25 at 17:03:19","Made available in DSpace on 2020-08-26T21:53:56Z (GMT). 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In particular, epitaxially growing high-quality (Al)GaN layers on foreign substrates, forming low-resistance ohmic contacts on (Al)GaN materials, properly passivating (Al)GaN surfaces, and reducing leakage currents are of great importance. In this dissertation, these challenges are individually addressed along with respective detailed studies. It is shown that a low GaN in-plane tensile strain allows a higher 2D electron gas mobility due to the alleviated interface roughness scattering. In addition, an ohmic contact specific resistance of 4 × 10-6 Ω–cm2 with Ti/Al/Ni/Au metal stacks has been achieved by three-step rapid thermal annealing. Furthermore, it is revealed that annealed, thin-Al2O3 dielectric is an effective (Al)GaN surface passivation alternative for minimizing passivation-associated parasitic capacitance, yet non-ideal for significantly suppressing gate leakage current in metal-insulator-semiconductor structures due to the governing trap-assisted tunneling carrier transport mechanism. A 3.5 µm Schottky-gate AlGaN/GaN HEMT with VT and gm of -0.87 V and 131.67 mS/mm, respectively, at VDS = 3.5 V has been demonstrated. The measured high Schottky gate leakage current and OFF-state drain current are believed to be responsible for the large subthreshold swing and low drain current on/off ratio. A passivation-last process followed by post-metallization annealing is then utilized, which largely reduces the reverse biased Schottky-gate leakage current and OFF-state drain current, leading to a low subthreshold swing of 84.75 mV/dec and a high drain current on/off ratio of 2.1 × 107. Together, the presented results add constructive inputs to the realization of reliable AlGaN/GaN HEMTs on Si(111) towards reliable high-speed electronics.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2020-08-25 without embargo terms","The student, Hsuan-Ping Lee, accepted the attached license on 2020-01-29 at 15:47.","The student, Hsuan-Ping Lee, submitted this Dissertation for approval on 2020-01-29 at 15:50.","This Dissertation was approved for publication on 2020-01-31 at 10:09.","DSpace SAF Submission Ingestion Package generated from Vireo submission #14860 on 2020-08-25 at 17:03:19","Made available in DSpace on 2020-08-26T21:53:56Z (GMT). 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