{"id":{"repo_id":"unm","oai_identifier":"oai:digitalrepository.unm.edu:nsms_etds-1006"},"canonical_url":"https://search.dev.ndltd.org/etd/unm/oai:digitalrepository.unm.edu:nsms_etds-1006","repository":{"repo_id":"unm","name":"University of New Mexico","base_url":"https://digitalrepository.unm.edu/do/oai/"},"display":{"title":"Empirical correlation of minority carrier lifetime to detect density profile in germanium on silicon heteroepitaxy","abstract":"High-quality Ge-on-Si (GoS) heterostructures are pursued for many applications, including near infrared (NIR) photodetectors and integration with III-V films for multi-junction photovoltaics. However, challenges such as thermal expansion coefficient mismatch and lattice mismatch between Ge and Si often leads to a high density of defects which can propagate through any III-V material grown subsequently. Introducing annealing steps prior to and after full Ge island coalescence are found to reduce the defect density. It has been observed that the defect density in Ge also decreases with increasing dopant density in Si substrates, likely by the defect pinning near the Ge/Si interface by dopants. Using the effective minority carrier lifetime measured as a function of Ge film thickness, an empirical correlation is established between the minority carrier lifetime and the defect density in the Ge film as a function of distance from the Ge/Si interface and relating the surface recombination velocity on Ge film surface average lifetime within Ge film, and recombination velocity at the Ge/Si interface. Two photoconductance decay techniques were used in this work: quasi-steady-state photoconductance decay and microwave photoconductance decay. The interface recombination velocity for Ge films grown on low-doped, high resistivity (HDLR) and high-doped, low resistivity (LDHR) Si substrates were found to be 370 cm/sec and 0.22 sec/cm2, respectively. Also established is an empirical correlation between minority carrier lifetime of the Ge film (\\uf074Ge) and the defect density (\\uf072D) within the Ge film as a function of distance from the Ge/Si interface: \\uf074Ge = C/\\uf072D, where C is a proportionality constant and a fitting parameter which is determined to be 0.17 sec/cm2 and 0.22 sec/cm2 for Ge films grown on LDHR Si substrates and HDLR Si substrates, respectively.","abstract_html":"High-quality Ge-on-Si (GoS) heterostructures are pursued for many applications, including near infrared (NIR) photodetectors and integration with III-V films for multi-junction photovoltaics. However, challenges such as thermal expansion coefficient mismatch and lattice mismatch between Ge and Si often leads to a high density of defects which can propagate through any III-V material grown subsequently. Introducing annealing steps prior to and after full Ge island coalescence are found to reduce the defect density. It has been observed that the defect density in Ge also decreases with increasing dopant density in Si substrates, likely by the defect pinning near the Ge/Si interface by dopants. Using the effective minority carrier lifetime measured as a function of Ge film thickness, an empirical correlation is established between the minority carrier lifetime and the defect density in the Ge film as a function of distance from the Ge/Si interface and relating the surface recombination velocity on Ge film surface average lifetime within Ge film, and recombination velocity at the Ge/Si interface. Two photoconductance decay techniques were used in this work: quasi-steady-state photoconductance decay and microwave photoconductance decay. The interface recombination velocity for Ge films grown on low-doped, high resistivity (HDLR) and high-doped, low resistivity (LDHR) Si substrates were found to be 370 cm/sec and 0.22 sec/cm2, respectively. Also established is an empirical correlation between minority carrier lifetime of the Ge film (\\uf074Ge) and the defect density (\\uf072D) within the Ge film as a function of distance from the Ge/Si interface: \\uf074Ge = C/\\uf072D, where C is a proportionality constant and a fitting parameter which is determined to be 0.17 sec/cm2 and 0.22 sec/cm2 for Ge films grown on LDHR Si substrates and HDLR Si substrates, respectively.","abstract_has_math":false,"creators":["Sheng, Josephine"],"institution":null,"degree_name":"Nanoscience and Microsystems","degree_level":"Dissertation","degree_discipline":"Nanoscience and Microsystems","degree_department":null,"school":null,"contributors":["Han, Sang","Khrishna, Sanjay","Balakhrishnan, Ganesh","Datye, Abhaya"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2013,"date_issued":"2013-09-05T07:00:00Z","date_published":"2013-09-05T07:00:00Z","updated_at":"2026-07-24T05:26:42Z","subjects":["Germanium","Heteroepitaxy","Minority Carrier Lifetime","Defect Density"],"languages":["English"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalrepository.unm.edu/nsms_etds/7"],"render_values":[{"text":"https://digitalrepository.unm.edu/nsms_etds/7","href":"https://digitalrepository.unm.edu/nsms_etds/7","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/1928/23372","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Han, Sang","Khrishna, Sanjay","Balakhrishnan, Ganesh","Datye, Abhaya"]},{"key":"dc:creator","label":"Author","values":["Sheng, Josephine"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Nanoscience and Microsystems"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation","Doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Nanoscience and Microsystems"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Germanium","Heteroepitaxy","Minority Carrier Lifetime","Defect Density"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/1928/23372","https://digitalrepository.unm.edu/nsms_etds/7"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["High-quality Ge-on-Si (GoS) heterostructures are pursued for many applications, including near infrared (NIR) photodetectors and integration with III-V films for multi-junction photovoltaics. However, challenges such as thermal expansion coefficient mismatch and lattice mismatch between Ge and Si often leads to a high density of defects which can propagate through any III-V material grown subsequently. Introducing annealing steps prior to and after full Ge island coalescence are found to reduce the defect density. It has been observed that the defect density in Ge also decreases with increasing dopant density in Si substrates, likely by the defect pinning near the Ge/Si interface by dopants. Using the effective minority carrier lifetime measured as a function of Ge film thickness, an empirical correlation is established between the minority carrier lifetime and the defect density in the Ge film as a function of distance from the Ge/Si interface and relating the surface recombination velocity on Ge film surface average lifetime within Ge film, and recombination velocity at the Ge/Si interface. Two photoconductance decay techniques were used in this work: quasi-steady-state photoconductance decay and microwave photoconductance decay. The interface recombination velocity for Ge films grown on low-doped, high resistivity (HDLR) and high-doped, low resistivity (LDHR) Si substrates were found to be 370 cm/sec and 0.22 sec/cm2, respectively. Also established is an empirical correlation between minority carrier lifetime of the Ge film (\\uf074Ge) and the defect density (\\uf072D) within the Ge film as a function of distance from the Ge/Si interface: \\uf074Ge = C/\\uf072D, where C is a proportionality constant and a fitting parameter which is determined to be 0.17 sec/cm2 and 0.22 sec/cm2 for Ge films grown on LDHR Si substrates and HDLR Si substrates, respectively."]},{"key":"dc:title","label":"Title","values":["Empirical correlation of minority carrier lifetime to detect density profile in germanium on silicon heteroepitaxy"]}]}],"canonical_facts":{"dc:contributor":["Han, Sang","Khrishna, Sanjay","Balakhrishnan, Ganesh","Datye, Abhaya"],"dc:creator":["Sheng, Josephine"],"dc:description.abstract":["High-quality Ge-on-Si (GoS) heterostructures are pursued for many applications, including near infrared (NIR) photodetectors and integration with III-V films for multi-junction photovoltaics. However, challenges such as thermal expansion coefficient mismatch and lattice mismatch between Ge and Si often leads to a high density of defects which can propagate through any III-V material grown subsequently. Introducing annealing steps prior to and after full Ge island coalescence are found to reduce the defect density. It has been observed that the defect density in Ge also decreases with increasing dopant density in Si substrates, likely by the defect pinning near the Ge/Si interface by dopants. Using the effective minority carrier lifetime measured as a function of Ge film thickness, an empirical correlation is established between the minority carrier lifetime and the defect density in the Ge film as a function of distance from the Ge/Si interface and relating the surface recombination velocity on Ge film surface average lifetime within Ge film, and recombination velocity at the Ge/Si interface. Two photoconductance decay techniques were used in this work: quasi-steady-state photoconductance decay and microwave photoconductance decay. The interface recombination velocity for Ge films grown on low-doped, high resistivity (HDLR) and high-doped, low resistivity (LDHR) Si substrates were found to be 370 cm/sec and 0.22 sec/cm2, respectively. Also established is an empirical correlation between minority carrier lifetime of the Ge film (\\uf074Ge) and the defect density (\\uf072D) within the Ge film as a function of distance from the Ge/Si interface: \\uf074Ge = C/\\uf072D, where C is a proportionality constant and a fitting parameter which is determined to be 0.17 sec/cm2 and 0.22 sec/cm2 for Ge films grown on LDHR Si substrates and HDLR Si substrates, respectively."],"dc:identifier":["http://hdl.handle.net/1928/23372","https://digitalrepository.unm.edu/nsms_etds/7"],"dc:language":["English"],"dc:subject":["Germanium","Heteroepitaxy","Minority Carrier Lifetime","Defect Density"],"dc:title":["Empirical correlation of minority carrier lifetime to detect density profile in germanium on silicon heteroepitaxy"],"thesis:degree_discipline":["Nanoscience and Microsystems"],"thesis:degree_level":["Dissertation","Doctoral"],"thesis:degree_name":["Nanoscience and Microsystems"]},"updated_at":"2026-07-24T05:26:42Z"}