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Effects of Annealing Atmosphere on Electrical Performance and Stability of High-Mobility Indium-Gallium-Tin Oxide Thin-Film Transistors
Open AccessEditor’s ChoiceArticle

Electrical Performance and Stability Improvements of High-Mobility Indium–Gallium–Tin Oxide Thin-Film Transistors Using an Oxidized Aluminum Capping Layer of Optimal Thickness

School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 06972, Korea
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Electronics 2020, 9(12), 2196; https://doi.org/10.3390/electronics9122196
Received: 21 November 2020 / Revised: 10 December 2020 / Accepted: 17 December 2020 / Published: 20 December 2020
(This article belongs to the Special Issue Applications of Thin Films in Microelectronics)
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. View Full-Text
Keywords: In–Ga–Sn–O (IGTO), thin-film transistor (TFT), Al capping layer; optimal thickness; weakly bonded oxygen species In–Ga–Sn–O (IGTO), thin-film transistor (TFT), Al capping layer; optimal thickness; weakly bonded oxygen species
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MDPI and ACS Style

Cha, H.-S.; Jeong, H.-S.; Hwang, S.-H.; Lee, D.-H.; Kwon, H.-I. 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, 9, 2196. https://doi.org/10.3390/electronics9122196

AMA Style

Cha H-S, Jeong H-S, Hwang S-H, Lee D-H, Kwon H-I. 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; 9(12):2196. https://doi.org/10.3390/electronics9122196

Chicago/Turabian Style

Cha, Hyun-Seok; Jeong, Hwan-Seok; Hwang, Seong-Hyun; Lee, Dong-Ho; Kwon, Hyuck-In. 2020. "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 9, no. 12: 2196. https://doi.org/10.3390/electronics9122196

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