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Park JM, Lee H, Lee G, Jang SC, Chang YH, Hong H, Chung KB, Lee KJ, Kim DH, Kim HS. Organic/Inorganic Hybrid Top-Gate Transistors with Ultrahigh Electron Mobility via Enhanced Electron Pathways. ACS APPLIED MATERIALS & INTERFACES 2023; 15:1525-1534. [PMID: 36538477 DOI: 10.1021/acsami.2c16881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The top-gate structure is currently adopted in various flat-panel displays because of its diverse advantages such as passivation from the external environment and process compatibility with industries. However, the mobility of the currently commercialized top-gate oxide thin-film transistors (TFTs) is insufficient to drive ultrahigh-resolution displays. Accordingly, this work suggests metal-capped Zn-Ba-Sn-O transistors with top-gate structures for inducing mobility-enhancing effects. The fabricated top-gate device contains para-xylylene (PPx), which is deposited by a low-temperature chemical vapor deposition (CVD) process, as a dielectric layer and exhibits excellent interfacial and dielectric properties. A technology computer-aided design (TCAD) device simulation reveals that the mobility enhancement in the Al-capped (Zn,Ba)SnO3 (ZBTO) TFT is attributed not only to the increase in the electron concentration, which is induced by band engineering due to the Al work function but also to the increased electron velocity due to the redistribution of the lateral electric field. As a result, the mobility of the Al-capped top-gate ZBTO device is 5 times higher (∼110 cm2/Vs) than that of the reference device. These results demonstrate the applicability of top-gate oxide TFTs with ultrahigh mobility in a wide range of applications, such as for high-resolution, large-area, and flexible displays.
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Affiliation(s)
- Ji-Min Park
- Department of Materials Science and Engineering, Chungnam National University, Daejeon34134, Republic of Korea
| | - Hyunkyu Lee
- School of Electrical Engineering, Kookmin University, Seoul02707, Republic of Korea
| | - GunOh Lee
- Department of Chemical Engineering & Applied Chemistry, Chungnam National University, Daejeon34134, Republic of Korea
| | - Seong Cheol Jang
- Department of Materials Science and Engineering, Chungnam National University, Daejeon34134, Republic of Korea
| | - Yun Hee Chang
- Department of Materials Science and Engineering, Chungnam National University, Daejeon34134, Republic of Korea
| | - Hyunmin Hong
- Division of Physics and Semiconductor Science, Dongguk University, Seoul04620, Republic of Korea
| | - Kwun-Bum Chung
- Division of Physics and Semiconductor Science, Dongguk University, Seoul04620, Republic of Korea
| | - Kyung Jin Lee
- Department of Chemical Engineering & Applied Chemistry, Chungnam National University, Daejeon34134, Republic of Korea
| | - Dae Hwan Kim
- School of Electrical Engineering, Kookmin University, Seoul02707, Republic of Korea
| | - Hyun-Suk Kim
- Department of Materials Science and Engineering, Chungnam National University, Daejeon34134, Republic of Korea
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Kim J, Park JB, Zheng D, Kim JS, Cheng Y, Park SK, Huang W, Marks TJ, Facchetti A. Readily Accessible Metallic Micro-Island Arrays for High-Performance Metal Oxide Thin-Film Transistors. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2205871. [PMID: 36039798 DOI: 10.1002/adma.202205871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 08/15/2022] [Indexed: 06/15/2023]
Abstract
Thin-film transistors using metal oxide semiconductors are essential in many unconventional electronic devices. Nevertheless, further advances will be necessary to broaden their technological appeal. Here, a new strategy is reported to achieve high-performance solution-processed metal oxide thin-film transistors (MOTFTs) by introducing a metallic micro-island array (M-MIA) on top of the MO back channel, where the MO is a-IGZO (amorphous indium-gallium-zinc-oxide). Here Al-MIAs are fabricated using honeycomb cinnamate cellulose films, created by a scalable breath-figure method, as a shadow mask. For IGZO TFTs, the electron mobility (µe ) increases from ≈3.6 cm2 V-1 s-1 to near 15.6 cm2 V-1 s-1 for optimal Al-MIA dimension/coverage of 1.25 µm/51%. The Al-MIA IGZO TFT performance is superior to that of controls using compact/planar Al layers (Al-PL TFTs) and Au-MIAs with the same channel coverage. Kelvin probe force microscopy and technology computer-aided design simulations reveal that charge transfer occurs between the Al and the IGZO channel which is optimized for specific Al-MIA dimensions/surface channel coverages. Furthermore, such Al-MIA IGZO TFTs with a high-k fluoride-doped alumina dielectric exhibit a maximum µe of >50.2 cm2 V-1 s-1 . This is the first demonstration of a micro-structured MO semiconductor heterojunction with submicrometer resolution metallic arrays for enhanced transistor performance and broad applicability to other devices.
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Affiliation(s)
- Jaehyun Kim
- Department of Chemistry and Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Joon Bee Park
- Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul, 06974, Korea
| | - Ding Zheng
- Department of Chemistry and Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Joon-Seok Kim
- Department of Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Yuhua Cheng
- School of Automation Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, Sichuan, 611731, China
| | - Sung Kyu Park
- Displays and Devices Research Lab. School of Electrical and Electronics Engineering, Chung-Ang University, Seoul, 06974, Korea
| | - Wei Huang
- Department of Chemistry and Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
- School of Automation Engineering, University of Electronic Science and Technology of China (UESTC), Chengdu, Sichuan, 611731, China
| | - Tobin J Marks
- Department of Chemistry and Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
| | - Antonio Facchetti
- Department of Chemistry and Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA
- Flexterra Corporation, 8025 Lamon Avenue, Skokie, IL, 60077, USA
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Characteristics and Electronic Band Alignment of a Transparent p-CuI/ n-SiZnSnO Heterojunction Diode with a High Rectification Ratio. NANOMATERIALS 2021; 11:nano11051237. [PMID: 34067221 PMCID: PMC8151173 DOI: 10.3390/nano11051237] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 04/30/2021] [Accepted: 05/05/2021] [Indexed: 11/26/2022]
Abstract
Transparent p-CuI/n-SiZnSnO (SZTO) heterojunction diodes are successfully fabricated by thermal evaporation of a (111) oriented p-CuI polycrystalline film on top of an amorphous n-SZTO film grown by the RF magnetron sputtering method. A nitrogen annealing process reduces ionized impurity scattering dominantly incurred by Cu vacancy and structural defects at the grain boundaries in the CuI film to result in improved diode performance; the current rectification ratio estimated at ±2 V is enhanced from ≈106 to ≈107. Various diode parameters, including ideality factor, reverse saturation current, offset current, series resistance, and parallel resistance, are estimated based on the Shockley diode equation. An energy band diagram exhibiting the type-II band alignment is proposed to explain the diode characteristics. The present p-CuI/n-SZTO diode can be a promising building block for constructing useful optoelectronic components such as a light-emitting diode and a UV photodetector.
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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 2020. [DOI: 10.3390/electronics9122196] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
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 (tAls) 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 cm2/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 tAl 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.
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Shin MG, Bae KH, Cha HS, Jeong HS, Kim DH, Kwon HI. Floating Ni Capping for High-Mobility p-Channel SnO Thin-Film Transistors. MATERIALS (BASEL, SWITZERLAND) 2020; 13:ma13143055. [PMID: 32650540 PMCID: PMC7411776 DOI: 10.3390/ma13143055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/26/2020] [Accepted: 07/07/2020] [Indexed: 06/11/2023]
Abstract
We utilized Ni as a floating capping layer in p-channel SnO thin-film transistors (TFTs) to improve their electrical performances. By utilizing the Ni as a floating capping layer, the p-channel SnO TFT showed enhanced mobility as high as 10.5 cm2·V-1·s-1. The increase in mobility was more significant as the length of Ni capping layer increased and the thickness of SnO active layer decreased. The observed phenomenon was possibly attributed to the changed vertical electric field distribution and increased hole concentration in the SnO channel by the floating Ni capping layer. Our experimental results demonstrate that incorporating the floating Ni capping layer on the channel layer is an effective method for increasing the field-effect mobility in p-channel SnO TFTs.
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Lee BH, Cho KS, Lee DY, Sohn A, Lee JY, Choo H, Park S, Kim SW, Kim S, Lee SY. Investigation on energy bandgap states of amorphous SiZnSnO thin films. Sci Rep 2019; 9:19246. [PMID: 31848440 PMCID: PMC6917747 DOI: 10.1038/s41598-019-55807-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 10/11/2019] [Indexed: 11/24/2022] Open
Abstract
The variation in energy bandgaps of amorphous oxide semiconducting SiZnSnO (a-SZTO) has been investigated by controlling the oxygen partial pressure (Op). The systematic change in Op during deposition has been used to control the electrical characteristics and energy bandgap of a-SZTO. As Op increased, the electrical properties degraded, while the energy bandgap increased systematically. This is mainly due to the change in the oxygen vacancy inside the a-SZTO thin film by controlling Op. Changes in oxygen vacancies have been observed by using X-ray photoelectron spectroscopy (XPS) and investigated by analyzing the variation in density of states (DOS) inside the energy bandgaps. In addition, energy bandgap parameters, such as valence band level, Fermi level, and energy bandgap, were extracted by using ultraviolet photoelectron spectroscopy, Kelvin probe force microscopy, and high-resolution electron energy loss spectroscopy. As a result, it was confirmed that the difference between the conduction band minimum and the Fermi level in the energy bandgap increased systematically as Op increases. This shows good agreement with the measured results of XPS and DOS analyses.
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Affiliation(s)
- Byeong Hyeon Lee
- Department of Microdevice Engineering, Korea University, Seoul, 136-701, South Korea.,Research Institute of Advanced Semiconductor Convergence Technology, Cheongju, 28503, South Korea
| | - Kyung-Sang Cho
- Imaging Device Laboratory, Samsung Advanced Institute of Technology, Suwon, 16678, South Korea
| | - Doo-Yong Lee
- Department of Physics, Pusan National University, Busan, 609-735, South Korea
| | - Ahrum Sohn
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Ji Ye Lee
- Department of Semiconductor Engineering, Cheongju University, Cheongju, 28503, South Korea
| | - Hyuck Choo
- Imaging Device Laboratory, Samsung Advanced Institute of Technology, Suwon, 16678, South Korea
| | - Sungkyun Park
- Department of Physics, Pusan National University, Busan, 609-735, South Korea
| | - Sang-Woo Kim
- School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Sangsig Kim
- Department of Microdevice Engineering, Korea University, Seoul, 136-701, South Korea
| | - Sang Yeol Lee
- Department of Semiconductor Engineering, Cheongju University, Cheongju, 28503, South Korea. .,Research Institute of Advanced Semiconductor Convergence Technology, Cheongju, 28503, South Korea.
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