Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness
We examined the effects of aluminum (Al) capping layer thickness on the electrical performance and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). The Al capping layers with thicknesses (<i>t</i><sub>Al</sub>s) of 3, 5, and 8 nm were d...
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MDPI AG
2020-12-01
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| Series: | Electronics |
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| Online Access: | https://www.mdpi.com/2079-9292/9/12/2196 |
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| author | Hyun-Seok Cha Hwan-Seok Jeong Seong-Hyun Hwang Dong-Ho Lee Hyuck-In Kwon |
| author_facet | Hyun-Seok Cha Hwan-Seok Jeong Seong-Hyun Hwang Dong-Ho Lee Hyuck-In Kwon |
| author_sort | Hyun-Seok Cha |
| collection | DOAJ |
| description | We examined the effects of aluminum (Al) capping layer thickness on the electrical performance and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). The Al capping layers with thicknesses (<i>t</i><sub>Al</sub>s) of 3, 5, and 8 nm were deposited, respectively, on top of the IGTO thin film by electron beam evaporation, and the IGTO TFTs without and with Al capping layers were subjected to thermal annealing at 200 °C for 1 h in ambient air. Among the IGTO TFTs without and with Al capping layers, the TFT with a 3 nm thick Al capping layer exhibited excellent electrical performance (field-effect mobility: 26.4 cm<sup>2</sup>/V s, subthreshold swing: 0.20 V/dec, and threshold voltage: −1.7 V) and higher electrical stability under positive and negative bias illumination stresses than other TFTs. To elucidate the physical mechanism responsible for the observed phenomenon, we compared the O1s spectra of the IGTO thin films without and with Al capping layers using X-ray photoelectron spectroscopy analyses. From the characterization results, it was observed that the weakly bonded oxygen-related components decreased from 25.0 to 10.0%, whereas the oxygen-deficient portion was maintained at 24.4% after the formation of the 3 nm thick Al capping layer. In contrast, a significant increase in the oxygen-deficient portion was observed after the formation of the Al capping layers having <i>t</i><sub>Al</sub> values greater than 3 nm. These results imply that the thicker Al capping layer has a stronger gathering power for the oxygen species, and that 3 nm is the optimum thickness of the Al capping layer, which can selectively remove the weakly bonded oxygen species acting as subgap tail states within the IGTO. The results of this study thus demonstrate that the formation of an Al capping layer with the optimal thickness is a practical and useful method to enhance the electrical performance and stability of high-mobility IGTO TFTs. |
| first_indexed | 2024-03-10T13:54:49Z |
| format | Article |
| id | doaj.art-ffd3e96207924926b6f179af4140bbd1 |
| institution | Directory Open Access Journal |
| issn | 2079-9292 |
| language | English |
| last_indexed | 2024-03-10T13:54:49Z |
| publishDate | 2020-12-01 |
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| record_format | Article |
| series | Electronics |
| spelling | doaj.art-ffd3e96207924926b6f179af4140bbd12023-11-21T01:44:32ZengMDPI AGElectronics2079-92922020-12-01912219610.3390/electronics9122196Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal ThicknessHyun-Seok Cha0Hwan-Seok Jeong1Seong-Hyun Hwang2Dong-Ho Lee3Hyuck-In Kwon4School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06972, KoreaSchool of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06972, KoreaSchool of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06972, KoreaSchool of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06972, KoreaSchool of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06972, KoreaWe examined the effects of aluminum (Al) capping layer thickness on the electrical performance and stability of high-mobility indium–gallium–tin oxide (IGTO) thin-film transistors (TFTs). The Al capping layers with thicknesses (<i>t</i><sub>Al</sub>s) of 3, 5, and 8 nm were deposited, respectively, on top of the IGTO thin film by electron beam evaporation, and the IGTO TFTs without and with Al capping layers were subjected to thermal annealing at 200 °C for 1 h in ambient air. Among the IGTO TFTs without and with Al capping layers, the TFT with a 3 nm thick Al capping layer exhibited excellent electrical performance (field-effect mobility: 26.4 cm<sup>2</sup>/V s, subthreshold swing: 0.20 V/dec, and threshold voltage: −1.7 V) and higher electrical stability under positive and negative bias illumination stresses than other TFTs. To elucidate the physical mechanism responsible for the observed phenomenon, we compared the O1s spectra of the IGTO thin films without and with Al capping layers using X-ray photoelectron spectroscopy analyses. From the characterization results, it was observed that the weakly bonded oxygen-related components decreased from 25.0 to 10.0%, whereas the oxygen-deficient portion was maintained at 24.4% after the formation of the 3 nm thick Al capping layer. In contrast, a significant increase in the oxygen-deficient portion was observed after the formation of the Al capping layers having <i>t</i><sub>Al</sub> values greater than 3 nm. These results imply that the thicker Al capping layer has a stronger gathering power for the oxygen species, and that 3 nm is the optimum thickness of the Al capping layer, which can selectively remove the weakly bonded oxygen species acting as subgap tail states within the IGTO. The results of this study thus demonstrate that the formation of an Al capping layer with the optimal thickness is a practical and useful method to enhance the electrical performance and stability of high-mobility IGTO TFTs.https://www.mdpi.com/2079-9292/9/12/2196In–Ga–Sn–O (IGTO), thin-film transistor (TFT), Al capping layeroptimal thicknessweakly bonded oxygen species |
| spellingShingle | Hyun-Seok Cha Hwan-Seok Jeong Seong-Hyun Hwang Dong-Ho Lee Hyuck-In Kwon Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness Electronics In–Ga–Sn–O (IGTO), thin-film transistor (TFT), Al capping layer optimal thickness weakly bonded oxygen species |
| title | Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness |
| title_full | Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness |
| title_fullStr | Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness |
| title_full_unstemmed | Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness |
| title_short | Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness |
| title_sort | electrical performance and stability improvements of high mobility indium gallium tin oxide thin film transistors using an oxidized aluminum capping layer of optimal thickness |
| topic | In–Ga–Sn–O (IGTO), thin-film transistor (TFT), Al capping layer optimal thickness weakly bonded oxygen species |
| url | https://www.mdpi.com/2079-9292/9/12/2196 |
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