{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/80990"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/80990","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Monolithic Integration of Thermally Stable Enhancement-Mode and Depletion-Mode Indium Phosphide HEMTs Utilizing Iridium-Gate and Silver-Ohmic Contact Techniques","abstract":"Excellent ohmic contacts based on Ge/Ag/Ni metallization have been developed for InAlAs/InGaAs/InP high electron mobility transistors (HEMTs) in a temperature range between 385 and 500°C for the first time. A minimum contact resistance of 0.06 O-mm was obtained at an annealing temperature of 425°C for 60 s in a rapid thermal annealing system. Thermal storage tests showed that the Ag-based ohmic contacts had far superior thermal stability than the conventional AuGe/Ni ohmic contacts for InAlAs/InGaAs/InP HEMTs. Auger electron spectroscopy and transmission electron microscopy study for both Ag-based and Au-based ohmic contacts confirmed that metal protrusions created by diffusion of contact metals linked the two-dimensional electron gas layer with the metal contacts to produce excellent ohmic contacts. The formation of liquid AuGe eutectic phase in the AuGe/Ni/Au metallization at relatively low temperature is believed to cause overannealing. The eutectic temperature of Ag-Ge is about 300°C higher than that of the Au-Ge system, leading to a much wider processing window and much better thermal stability for the Ge/Ag/Ni ohmic contacts. After a detailed electrical and microanalysis study of Shottky diodes based on Ir/Ti/Pt/Au metallization, a fabrication process for the realization of thermally stable InAlAs/InGaAs/InP enhancement-mode HEMTs based on annealed Ir-gate and Ge/Ag/Ni-ohmic contacts were developed subsequently. The enhancement-mode InAlAs/InGaAs/InP HEMTs with a gate-length of 0.1 mum demonstrated excellent DC and RF characteristics including: threshold voltage of 198 mV, Gm, max of 945 mS/mm, IDSS of 0.25 mA/mm, and fT of 205 GHz. Thermal stability study of these devices showed that no degradation of the extrinsic transconductance and drain current was observed at storage temperature of 215°C for a storing period of 96 h. At the same time, stable operation of the Ir/Ti/Pt/Au-gate contact was also obtained. Finally, by optimizing the HEMT layer structure and the doping concentration, monolithic integration of depletion-mode and enhancement-mode InAlAs/InGaAs/InP HEMTs were realized through the newly developed fabrication process based on Ge/Ag/Ni-ohmic and Ir-gate contact technologies, which are highly applicable to high speed integrated circuits.","abstract_html":"Excellent ohmic contacts based on Ge/Ag/Ni metallization have been developed for InAlAs/InGaAs/InP high electron mobility transistors (HEMTs) in a temperature range between 385 and 500°C for the first time. A minimum contact resistance of 0.06 O-mm was obtained at an annealing temperature of 425°C for 60 s in a rapid thermal annealing system. Thermal storage tests showed that the Ag-based ohmic contacts had far superior thermal stability than the conventional AuGe/Ni ohmic contacts for InAlAs/InGaAs/InP HEMTs. Auger electron spectroscopy and transmission electron microscopy study for both Ag-based and Au-based ohmic contacts confirmed that metal protrusions created by diffusion of contact metals linked the two-dimensional electron gas layer with the metal contacts to produce excellent ohmic contacts. The formation of liquid AuGe eutectic phase in the AuGe/Ni/Au metallization at relatively low temperature is believed to cause overannealing. The eutectic temperature of Ag-Ge is about 300°C higher than that of the Au-Ge system, leading to a much wider processing window and much better thermal stability for the Ge/Ag/Ni ohmic contacts. After a detailed electrical and microanalysis study of Shottky diodes based on Ir/Ti/Pt/Au metallization, a fabrication process for the realization of thermally stable InAlAs/InGaAs/InP enhancement-mode HEMTs based on annealed Ir-gate and Ge/Ag/Ni-ohmic contacts were developed subsequently. The enhancement-mode InAlAs/InGaAs/InP HEMTs with a gate-length of 0.1 mum demonstrated excellent DC and RF characteristics including: threshold voltage of 198 mV, Gm, max of 945 mS/mm, IDSS of 0.25 mA/mm, and fT of 205 GHz. Thermal stability study of these devices showed that no degradation of the extrinsic transconductance and drain current was observed at storage temperature of 215°C for a storing period of 96 h. At the same time, stable operation of the Ir/Ti/Pt/Au-gate contact was also obtained. Finally, by optimizing the HEMT layer structure and the doping concentration, monolithic integration of depletion-mode and enhancement-mode InAlAs/InGaAs/InP HEMTs were realized through the newly developed fabrication process based on Ge/Ag/Ni-ohmic and Ir-gate contact technologies, which are highly applicable to high speed integrated circuits.","abstract_has_math":false,"creators":["Zhao, Weifeng"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Electrical and Computer Engineering","degree_department":null,"school":null,"contributors":["Adesida, Ilesanmi"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T20:09:08Z","date_published":"2015-09-25T20:09:08Z","updated_at":"2026-07-22T22:26:15Z","subjects":["Engineering, Materials Science"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3243043"],"render_values":[{"text":"(MiAaPQ)AAI3243043","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/80990","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Adesida, Ilesanmi"]},{"key":"dc:creator","label":"Author","values":["Zhao, Weifeng"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T20:09:08Z","10000-01-01","2006"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical and Computer Engineering"]},{"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":["Engineering, Materials Science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/80990","(MiAaPQ)AAI3243043"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Excellent ohmic contacts based on Ge/Ag/Ni metallization have been developed for InAlAs/InGaAs/InP high electron mobility transistors (HEMTs) in a temperature range between 385 and 500°C for the first time. A minimum contact resistance of 0.06 O-mm was obtained at an annealing temperature of 425°C for 60 s in a rapid thermal annealing system. Thermal storage tests showed that the Ag-based ohmic contacts had far superior thermal stability than the conventional AuGe/Ni ohmic contacts for InAlAs/InGaAs/InP HEMTs. Auger electron spectroscopy and transmission electron microscopy study for both Ag-based and Au-based ohmic contacts confirmed that metal protrusions created by diffusion of contact metals linked the two-dimensional electron gas layer with the metal contacts to produce excellent ohmic contacts. The formation of liquid AuGe eutectic phase in the AuGe/Ni/Au metallization at relatively low temperature is believed to cause overannealing. The eutectic temperature of Ag-Ge is about 300°C higher than that of the Au-Ge system, leading to a much wider processing window and much better thermal stability for the Ge/Ag/Ni ohmic contacts. After a detailed electrical and microanalysis study of Shottky diodes based on Ir/Ti/Pt/Au metallization, a fabrication process for the realization of thermally stable InAlAs/InGaAs/InP enhancement-mode HEMTs based on annealed Ir-gate and Ge/Ag/Ni-ohmic contacts were developed subsequently. The enhancement-mode InAlAs/InGaAs/InP HEMTs with a gate-length of 0.1 mum demonstrated excellent DC and RF characteristics including: threshold voltage of 198 mV, Gm, max of 945 mS/mm, IDSS of 0.25 mA/mm, and fT of 205 GHz. Thermal stability study of these devices showed that no degradation of the extrinsic transconductance and drain current was observed at storage temperature of 215°C for a storing period of 96 h. At the same time, stable operation of the Ir/Ti/Pt/Au-gate contact was also obtained. Finally, by optimizing the HEMT layer structure and the doping concentration, monolithic integration of depletion-mode and enhancement-mode InAlAs/InGaAs/InP HEMTs were realized through the newly developed fabrication process based on Ge/Ag/Ni-ohmic and Ir-gate contact technologies, which are highly applicable to high speed integrated circuits.","Made available in DSpace on 2015-09-25T20:09:08Z (GMT). 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A minimum contact resistance of 0.06 O-mm was obtained at an annealing temperature of 425°C for 60 s in a rapid thermal annealing system. Thermal storage tests showed that the Ag-based ohmic contacts had far superior thermal stability than the conventional AuGe/Ni ohmic contacts for InAlAs/InGaAs/InP HEMTs. Auger electron spectroscopy and transmission electron microscopy study for both Ag-based and Au-based ohmic contacts confirmed that metal protrusions created by diffusion of contact metals linked the two-dimensional electron gas layer with the metal contacts to produce excellent ohmic contacts. The formation of liquid AuGe eutectic phase in the AuGe/Ni/Au metallization at relatively low temperature is believed to cause overannealing. The eutectic temperature of Ag-Ge is about 300°C higher than that of the Au-Ge system, leading to a much wider processing window and much better thermal stability for the Ge/Ag/Ni ohmic contacts. After a detailed electrical and microanalysis study of Shottky diodes based on Ir/Ti/Pt/Au metallization, a fabrication process for the realization of thermally stable InAlAs/InGaAs/InP enhancement-mode HEMTs based on annealed Ir-gate and Ge/Ag/Ni-ohmic contacts were developed subsequently. The enhancement-mode InAlAs/InGaAs/InP HEMTs with a gate-length of 0.1 mum demonstrated excellent DC and RF characteristics including: threshold voltage of 198 mV, Gm, max of 945 mS/mm, IDSS of 0.25 mA/mm, and fT of 205 GHz. Thermal stability study of these devices showed that no degradation of the extrinsic transconductance and drain current was observed at storage temperature of 215°C for a storing period of 96 h. At the same time, stable operation of the Ir/Ti/Pt/Au-gate contact was also obtained. Finally, by optimizing the HEMT layer structure and the doping concentration, monolithic integration of depletion-mode and enhancement-mode InAlAs/InGaAs/InP HEMTs were realized through the newly developed fabrication process based on Ge/Ag/Ni-ohmic and Ir-gate contact technologies, which are highly applicable to high speed integrated circuits.","Made available in DSpace on 2015-09-25T20:09:08Z (GMT). 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