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Published in the Optical Materials Science Journal Advanced Optical Materials (IF: 8.0, Top 8.0% in JCR Ranking)

 (Left) Kim Eun-Ha, Integrated Master's and Doctoral Program; (Right) Professor Ha Tae-Jun

Professor Ha Tae-Jun (Department of Electronic Materials Engineering) and his research team at our university have successfully developed a Cd-doped indium-gallium-zinc oxide (IGZO) phototransistor with enhanced responsiveness in the visible light spectrum. They also designed a heater-integrated structure, effectively improving the recovery characteristics of the phototransistor.

The results of this study were published in Advanced Optical Materials (IF: 8.0, Top 8.0% in JCR ranking), a leading journal in the field of optical materials science published by Wiley. The paper is titled “Heater-Embedded Visible-Light Phototransistor Based on Cd-Doped IGZO Film Fabricated through Microwave-Assisted Sol-Gel Process.”

 (Reference: https://doi.org/10.1002/adom.202402171)

Recently, oxide semiconductor IGZO has been widely studied as a channel layer material for phototransistors due to its excellent responsiveness in the ultra-violet (UV) range and its high external quantum efficiency (EQE). However, its low responsiveness in the visible light range, caused by its wide bandgap, and the persistent photoconductivity (PPC) characteristic of oxide semiconductors present challenges for its practical application as a visible-light phototransistor. In response, Professor Ha Tae-Jun (Department of Electronic Materials Engineering) and his research team doped IGZO with the metal ion Cd, which reduces its bandgap and promotes the formation of oxygen vacancies, thereby facilitating visible light absorption. Additionally, they significantly improved the recovery characteristics of the phototransistor through Joule heating. Notably, the team successfully developed a device that simultaneously functions as a heater and a phototransistor by utilizing an indium-tin oxide (ITO) substrate, which serves both as the gate electrode of the phototransistor and as a Joule heating element. The fabricated Cd-doped IGZO phototransistor demonstrated a significant improvement in visible light responsiveness, increasing from 1.89 A/W to 22.6 A/W compared to conventional IGZO phototransistors. Additionally, it exhibited excellent linearity in photoresponse with respect to light intensity, highlighting its reliability in sensing performance. Furthermore, the Joule heating effect of the ITO substrate significantly reduced the recovery time from approximately 1,300 seconds to just 12 seconds, demonstrating the potential for practical applications of oxide semiconductor-based phototransistors.

Analysis of visible light sensing performance and recovery characteristics of heater-integrated Cd-doped IGZO phototransistors

This study, conducted solely by Professor Ha Tae-Jun's research team, is a result of the Interactive Display Research Center, led by Professor Ha as its director, and was supported by the University's Innovative Future Challenge Project. Additionally, the study was conducted with support from the Carbon Neutral Industrial Core Technology Development Program, overseen by the Ministry of Trade, Industry, and Energy. This program, carried out over eight years from 2023 to 2030, involves Samsung Display as the primary demand partner. Professor Ha Tae-Jun's research team is responsible for developing oxide semiconductor transistor devices and processes as part of this initiative.

Professor Ha Tae-Jun's research team conducts extensive studies on next-generation electronic devices based on advanced semiconductor materials. Their work includes publishing over 60 papers in SCI journals and securing more than 30 international and domestic patents, with a focus on oxide semiconductors and related technologies. Additionally, Kim Eun-Ha, the first author, achieved the outstanding accomplishment of publishing a paper in a top-tier international journal during her first semester in the integrated master's and doctoral program.