{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/80922"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/80922","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Submicron Scaling of Indium Phosphide/indium Gallium Arsenide Heterojunction Bipolar Transistors Toward Terahertz Bandwidths","abstract":"This work extends the operating speed of InP HBTs to frequencies of fT = 604 GHz though aggressive delay reductions and advanced fabrication processes. Delay reduction is employed by a combination of vertical scaling, lateral scaling, and epitaxial engineering to reduce the transit and charging times of the HBT. The device fabrication process is designed to allow deep submicron scaling of transistor dimensions, with HBTs as small as 0.25 x 0.85 mum2 fabricated. The presented devices are thoroughly modeled to characterize small signal and thermal performance. In order to quantify the effects of each method of delay reduction, an accurate model of small-signal HBT behavior is developed, allowing for complete discretization of device delay times. Device reliability is also investigated, focusing on junction temperatures of high current density SHBTs. A novel method for determining the thermal resistance of an HBT is presented, correcting the considerable error obtained by classical theoretical predictions. The relationships between junction temperature and cutoff frequency, and the thermal resistance dependence on device size are presented. Finally, extrapolating from the characteristics measured and extracted from fabricated HBTs, obstacles to achieving THz operation are identified, and specific steps are outlined to allow the InP/InGaAs material system to achieve its full potential as a candidate for realizing a THz transistor.","abstract_html":"This work extends the operating speed of InP HBTs to frequencies of fT = 604 GHz though aggressive delay reductions and advanced fabrication processes. Delay reduction is employed by a combination of vertical scaling, lateral scaling, and epitaxial engineering to reduce the transit and charging times of the HBT. The device fabrication process is designed to allow deep submicron scaling of transistor dimensions, with HBTs as small as 0.25 x 0.85 mum2 fabricated. The presented devices are thoroughly modeled to characterize small signal and thermal performance. In order to quantify the effects of each method of delay reduction, an accurate model of small-signal HBT behavior is developed, allowing for complete discretization of device delay times. Device reliability is also investigated, focusing on junction temperatures of high current density SHBTs. A novel method for determining the thermal resistance of an HBT is presented, correcting the considerable error obtained by classical theoretical predictions. The relationships between junction temperature and cutoff frequency, and the thermal resistance dependence on device size are presented. Finally, extrapolating from the characteristics measured and extracted from fabricated HBTs, obstacles to achieving THz operation are identified, and specific steps are outlined to allow the InP/InGaAs material system to achieve its full potential as a candidate for realizing a THz transistor.","abstract_has_math":false,"creators":["Hafez, Walid Mahmoud"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Electrical Engineering","degree_department":null,"school":null,"contributors":["Feng, Milton"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-25T20:08:51Z","date_published":"2015-09-25T20:08:51Z","updated_at":"2026-07-22T22:26:15Z","subjects":["Engineering, Electronics and Electrical"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(MiAaPQ)AAI3199008"],"render_values":[{"text":"(MiAaPQ)AAI3199008","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/80922","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Feng, Milton"]},{"key":"dc:creator","label":"Author","values":["Hafez, Walid Mahmoud"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-25T20:08:51Z","10000-01-01","2005"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical 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, Electronics and Electrical"]}]},{"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/2142/80922","(MiAaPQ)AAI3199008"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["This work extends the operating speed of InP HBTs to frequencies of fT = 604 GHz though aggressive delay reductions and advanced fabrication processes. Delay reduction is employed by a combination of vertical scaling, lateral scaling, and epitaxial engineering to reduce the transit and charging times of the HBT. The device fabrication process is designed to allow deep submicron scaling of transistor dimensions, with HBTs as small as 0.25 x 0.85 mum2 fabricated. The presented devices are thoroughly modeled to characterize small signal and thermal performance. In order to quantify the effects of each method of delay reduction, an accurate model of small-signal HBT behavior is developed, allowing for complete discretization of device delay times. Device reliability is also investigated, focusing on junction temperatures of high current density SHBTs. A novel method for determining the thermal resistance of an HBT is presented, correcting the considerable error obtained by classical theoretical predictions. The relationships between junction temperature and cutoff frequency, and the thermal resistance dependence on device size are presented. Finally, extrapolating from the characteristics measured and extracted from fabricated HBTs, obstacles to achieving THz operation are identified, and specific steps are outlined to allow the InP/InGaAs material system to achieve its full potential as a candidate for realizing a THz transistor.","Made available in DSpace on 2015-09-25T20:08:51Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3199008.pdf: 2676760 bytes, checksum: e1354e03ea6cfbd34a1ee9aef6b805eb (MD5) Previous issue date: 2005","Embargo set by: Seth Robbins for item 82204 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","92 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005."]},{"key":"dc:title","label":"Title","values":["Submicron Scaling of Indium Phosphide/indium Gallium Arsenide Heterojunction Bipolar Transistors Toward Terahertz Bandwidths"]}]}],"canonical_facts":{"dc:contributor":["Feng, Milton"],"dc:creator":["Hafez, Walid Mahmoud"],"dc:date":["2015-09-25T20:08:51Z","10000-01-01","2005"],"dc:description":["This work extends the operating speed of InP HBTs to frequencies of fT = 604 GHz though aggressive delay reductions and advanced fabrication processes. Delay reduction is employed by a combination of vertical scaling, lateral scaling, and epitaxial engineering to reduce the transit and charging times of the HBT. The device fabrication process is designed to allow deep submicron scaling of transistor dimensions, with HBTs as small as 0.25 x 0.85 mum2 fabricated. The presented devices are thoroughly modeled to characterize small signal and thermal performance. In order to quantify the effects of each method of delay reduction, an accurate model of small-signal HBT behavior is developed, allowing for complete discretization of device delay times. Device reliability is also investigated, focusing on junction temperatures of high current density SHBTs. A novel method for determining the thermal resistance of an HBT is presented, correcting the considerable error obtained by classical theoretical predictions. The relationships between junction temperature and cutoff frequency, and the thermal resistance dependence on device size are presented. Finally, extrapolating from the characteristics measured and extracted from fabricated HBTs, obstacles to achieving THz operation are identified, and specific steps are outlined to allow the InP/InGaAs material system to achieve its full potential as a candidate for realizing a THz transistor.","Made available in DSpace on 2015-09-25T20:08:51Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3199008.pdf: 2676760 bytes, checksum: e1354e03ea6cfbd34a1ee9aef6b805eb (MD5) Previous issue date: 2005","Embargo set by: Seth Robbins for item 82204 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","92 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005."],"dc:identifier":["http://hdl.handle.net/2142/80922","(MiAaPQ)AAI3199008"],"dc:language":["eng"],"dc:subject":["Engineering, Electronics and Electrical"],"dc:title":["Submicron Scaling of Indium Phosphide/indium Gallium Arsenide Heterojunction Bipolar Transistors Toward Terahertz Bandwidths"],"dc:type":["text"],"thesis:degree_discipline":["Electrical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:15Z"}