Microstructure and conductance-slope of InAs/GaSb tunnel diodes
InAs/GaSb and similar materials systems have generated great interest as a heterojunction for tunnel field effect transistors (TFETs) due to favorable band alignment. However, little is currently understood about how such TFETs are affected by materials defects and nonidealities. We present measurem...
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| Format: | Article |
| Language: | en_US |
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American Institute of Physics (AIP)
2014
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| Online Access: | http://hdl.handle.net/1721.1/91915 https://orcid.org/0000-0002-1891-1959 https://orcid.org/0000-0001-6823-3837 |
| _version_ | 1826212628712652800 |
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| author | Fitzgerald, Eugene A. Iutzi, Ryan (Ryan Michael) |
| author2 | Massachusetts Institute of Technology. Department of Materials Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Materials Science and Engineering Fitzgerald, Eugene A. Iutzi, Ryan (Ryan Michael) |
| author_sort | Fitzgerald, Eugene A. |
| collection | MIT |
| description | InAs/GaSb and similar materials systems have generated great interest as a heterojunction for tunnel field effect transistors (TFETs) due to favorable band alignment. However, little is currently understood about how such TFETs are affected by materials defects and nonidealities. We present measurements of the conductance slope for various InAs/GaSb heterojunctions via two-terminal electrical measurements, which removes three-terminal parasitics and enables direct study on the effect of microstructure on tunnelling. Using this, we can predict how subthreshold swings in TFETs can depend on microstructure. We also demonstrate growth and electrical characterization for structures grown by metalorganic chemical vapor deposition (MOCVD)—a generally more scalable process compared with molecular beam epitaxy (MBE). We determine that misfit dislocations and point defects near the interface can lead to energy states in the band-gap and local band bending that result in trap-assisted leakage routes and nonuniform band alignment across the junction area that lower the steepness of the conductance slope. Despite the small lattice mismatch, misfit dislocations still form in InAs on GaSb due to relaxation as a result of large strain from intermixed compositions. This can be circumvented by growing GaSb on InAs, straining the GaSb underlayer, or lowering the InAs growth temperature in the region of the interface. The conductance slope can also be improved by annealing the samples at higher temperatures, which we believe acts to annihilate point defects and average out major fluctuations in band alignment across the interface. Using a combination of these techniques, we can greatly improve the steepness of the conductance slope which could result in steeper subthreshold swings in TFETs in the future. |
| first_indexed | 2024-09-23T15:30:47Z |
| format | Article |
| id | mit-1721.1/91915 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T15:30:47Z |
| publishDate | 2014 |
| publisher | American Institute of Physics (AIP) |
| record_format | dspace |
| spelling | mit-1721.1/919152022-09-29T14:48:23Z Microstructure and conductance-slope of InAs/GaSb tunnel diodes Fitzgerald, Eugene A. Iutzi, Ryan (Ryan Michael) Massachusetts Institute of Technology. Department of Materials Science and Engineering Iutzi, Ryan (Ryan Michael) Fitzgerald, Eugene A. InAs/GaSb and similar materials systems have generated great interest as a heterojunction for tunnel field effect transistors (TFETs) due to favorable band alignment. However, little is currently understood about how such TFETs are affected by materials defects and nonidealities. We present measurements of the conductance slope for various InAs/GaSb heterojunctions via two-terminal electrical measurements, which removes three-terminal parasitics and enables direct study on the effect of microstructure on tunnelling. Using this, we can predict how subthreshold swings in TFETs can depend on microstructure. We also demonstrate growth and electrical characterization for structures grown by metalorganic chemical vapor deposition (MOCVD)—a generally more scalable process compared with molecular beam epitaxy (MBE). We determine that misfit dislocations and point defects near the interface can lead to energy states in the band-gap and local band bending that result in trap-assisted leakage routes and nonuniform band alignment across the junction area that lower the steepness of the conductance slope. Despite the small lattice mismatch, misfit dislocations still form in InAs on GaSb due to relaxation as a result of large strain from intermixed compositions. This can be circumvented by growing GaSb on InAs, straining the GaSb underlayer, or lowering the InAs growth temperature in the region of the interface. The conductance slope can also be improved by annealing the samples at higher temperatures, which we believe acts to annihilate point defects and average out major fluctuations in band alignment across the interface. Using a combination of these techniques, we can greatly improve the steepness of the conductance slope which could result in steeper subthreshold swings in TFETs in the future. National Science Foundation (U.S.). Center for Energy Efficient Electronics Science (Award 0939514) Natural Sciences and Engineering Research Council of Canada (Postgraduate M Scholarship) 2014-11-26T14:24:40Z 2014-11-26T14:24:40Z 2014-06 2013-12 Article http://purl.org/eprint/type/JournalArticle 0021-8979 1089-7550 http://hdl.handle.net/1721.1/91915 Iutzi, Ryan M., and Eugene A. Fitzgerald. “Microstructure and Conductance-Slope of InAs/GaSb Tunnel Diodes.” Journal of Applied Physics 115, no. 23 (June 21, 2014): 234503. https://orcid.org/0000-0002-1891-1959 https://orcid.org/0000-0001-6823-3837 en_US http://dx.doi.org/10.1063/1.4883756 Journal of Applied Physics Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf American Institute of Physics (AIP) arXiv |
| spellingShingle | Fitzgerald, Eugene A. Iutzi, Ryan (Ryan Michael) Microstructure and conductance-slope of InAs/GaSb tunnel diodes |
| title | Microstructure and conductance-slope of InAs/GaSb tunnel diodes |
| title_full | Microstructure and conductance-slope of InAs/GaSb tunnel diodes |
| title_fullStr | Microstructure and conductance-slope of InAs/GaSb tunnel diodes |
| title_full_unstemmed | Microstructure and conductance-slope of InAs/GaSb tunnel diodes |
| title_short | Microstructure and conductance-slope of InAs/GaSb tunnel diodes |
| title_sort | microstructure and conductance slope of inas gasb tunnel diodes |
| url | http://hdl.handle.net/1721.1/91915 https://orcid.org/0000-0002-1891-1959 https://orcid.org/0000-0001-6823-3837 |
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