Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon
Preserving a contamination-free metal–semiconductor interface in β-Ga2O3 is critical to achieve consistently low resistance (< 1 Ω-mm) ohmic contacts. Here, we report a scanning transmission electron microscopy study on the variation in Ti/Au ohmic contact quality to (010) β-Ga2O3 in a convention...
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AIP Publishing LLC
2025-06-01
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| Series: | APL Materials |
| Online Access: | http://dx.doi.org/10.1063/5.0276786 |
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| author | Naomi Pieczulewski Kathleen T. Smith Corey M. Efaw Arjan Singh Cameron A. Gorsak Joshua T. Buontempo Jesse Wensel Kathy Azizie Katie Gann Michael O. Thompson Darrell G. Schlom Farhan Rana Hari P. Nair Steven M. Hues Elton Graugnard Paul H. Davis Debdeep Jena Huili Grace Xing David A. Muller |
| author_facet | Naomi Pieczulewski Kathleen T. Smith Corey M. Efaw Arjan Singh Cameron A. Gorsak Joshua T. Buontempo Jesse Wensel Kathy Azizie Katie Gann Michael O. Thompson Darrell G. Schlom Farhan Rana Hari P. Nair Steven M. Hues Elton Graugnard Paul H. Davis Debdeep Jena Huili Grace Xing David A. Muller |
| author_sort | Naomi Pieczulewski |
| collection | DOAJ |
| description | Preserving a contamination-free metal–semiconductor interface in β-Ga2O3 is critical to achieve consistently low resistance (< 1 Ω-mm) ohmic contacts. Here, we report a scanning transmission electron microscopy study on the variation in Ti/Au ohmic contact quality to (010) β-Ga2O3 in a conventional lift-off vs a metal-first process. We observe a thin ∼1 nm carbon barrier between the Ti and Ga2O3 in a non-conductive contact fabricated by a conventional lift-off process, which we attribute to photoresist residue, not previously detected by x-ray photoelectron spectroscopy due to the thinness and patchy coverage of the carbon layer, as well as roughness of the Ga2O3 surface. This thin carbon barrier is confirmed by electron energy loss spectroscopy and atomic force microscopy-infrared spectroscopy. We believe that the presence of the thin and patchy carbon layer leads to the highly inconsistent contact behavior in previous reports on non-alloyed contacts. Adventitious carbon is also observed in a conductive ohmic contact metal-first processing on an as-grown sample. We find that a five minute active oxygen descum is sufficient to remove this carbon on as-grown samples, further improving the ohmic behavior and reducing the contact resistance Rc to 0.06 Ω-mm. We also show that an hour long UV-ozone treatment of the Ga2O3 surface can eliminate carbon residue from the lift-off processing, resulting in a low Rc of 0.05 Ω-mm. |
| format | Article |
| id | doaj-art-c612752ec3f84881b61cd1a63d5ca8bd |
| institution | Kabale University |
| issn | 2166-532X |
| language | English |
| publishDate | 2025-06-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | APL Materials |
| spelling | doaj-art-c612752ec3f84881b61cd1a63d5ca8bd2025-08-20T03:30:37ZengAIP Publishing LLCAPL Materials2166-532X2025-06-01136061122061122-1210.1063/5.0276786Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbonNaomi Pieczulewski0Kathleen T. Smith1Corey M. Efaw2Arjan Singh3Cameron A. Gorsak4Joshua T. Buontempo5Jesse Wensel6Kathy Azizie7Katie Gann8Michael O. Thompson9Darrell G. Schlom10Farhan Rana11Hari P. Nair12Steven M. Hues13Elton Graugnard14Paul H. Davis15Debdeep Jena16Huili Grace Xing17David A. Muller18Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USASchool of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USAMicron School of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, USASchool of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USAMicron Technology, 8000 S Federal Way, Boise, Idaho 83707, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USASchool of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USAMicron School of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, USAMicron School of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, USAMicron School of Materials Science and Engineering, Boise State University, Boise, Idaho 83725, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USADepartment of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USASchool of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USAPreserving a contamination-free metal–semiconductor interface in β-Ga2O3 is critical to achieve consistently low resistance (< 1 Ω-mm) ohmic contacts. Here, we report a scanning transmission electron microscopy study on the variation in Ti/Au ohmic contact quality to (010) β-Ga2O3 in a conventional lift-off vs a metal-first process. We observe a thin ∼1 nm carbon barrier between the Ti and Ga2O3 in a non-conductive contact fabricated by a conventional lift-off process, which we attribute to photoresist residue, not previously detected by x-ray photoelectron spectroscopy due to the thinness and patchy coverage of the carbon layer, as well as roughness of the Ga2O3 surface. This thin carbon barrier is confirmed by electron energy loss spectroscopy and atomic force microscopy-infrared spectroscopy. We believe that the presence of the thin and patchy carbon layer leads to the highly inconsistent contact behavior in previous reports on non-alloyed contacts. Adventitious carbon is also observed in a conductive ohmic contact metal-first processing on an as-grown sample. We find that a five minute active oxygen descum is sufficient to remove this carbon on as-grown samples, further improving the ohmic behavior and reducing the contact resistance Rc to 0.06 Ω-mm. We also show that an hour long UV-ozone treatment of the Ga2O3 surface can eliminate carbon residue from the lift-off processing, resulting in a low Rc of 0.05 Ω-mm.http://dx.doi.org/10.1063/5.0276786 |
| spellingShingle | Naomi Pieczulewski Kathleen T. Smith Corey M. Efaw Arjan Singh Cameron A. Gorsak Joshua T. Buontempo Jesse Wensel Kathy Azizie Katie Gann Michael O. Thompson Darrell G. Schlom Farhan Rana Hari P. Nair Steven M. Hues Elton Graugnard Paul H. Davis Debdeep Jena Huili Grace Xing David A. Muller Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon APL Materials |
| title | Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon |
| title_full | Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon |
| title_fullStr | Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon |
| title_full_unstemmed | Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon |
| title_short | Achieving 0.05 Ω-mm contact resistance in non-alloyed Ti/Au ohmics to β-Ga2O3 by removing surface carbon |
| title_sort | achieving 0 05 ω mm contact resistance in non alloyed ti au ohmics to β ga2o3 by removing surface carbon |
| url | http://dx.doi.org/10.1063/5.0276786 |
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