Reviewed by Lexie CornerApr 26 2024
In a recent study published in the journal Nature, scientists at the Pohang University of Science and Technology, University of Electronic Science and Technology, and Korea Research Institute of Standards and Science have made an effort to create highly stable and high-performance p-type thin-film transistors (TFT) used in computers and cell phones.
In a recent study published in the journal Nature, scientists at the Pohang University of Science and Technology, University of Electronic Science and Technology, and Korea Research Institute of Standards and Science have made an effort to create highly stable and high-performance p-type thin-film transistors (TFT) used in computers and cell phones.
The creation of a tellurium-selenium composite oxide semiconductor material was a joint effort between Professor Yong-Young Noh of Pohang University of Science and Technology (POSTECH), Drs. Ao Liu and Huihui Zhu, who were postdoctoral researchers in the Department of Chemical Engineering at POSTECH and are now professors at the University of Electronic Science and Technology of China, Dr. Yong-Sung Kim of the Korea Research Institute of Standards and Science, and Dr. Min Gyu Kim of the Pohang Accelerator Laboratory.
Nearly all electronic devices, including computers, cell phones, and cars, depend on semiconductors. Semiconductors fall into two primary categories: crystalline and amorphous. Crystalline semiconductors have an ordered atomic or molecular structure—amorphous semiconductors lack this regularity. As such, amorphous semiconductors are less expensive and require less complicated fabrication techniques than their crystalline counterparts. They usually perform less well electrically.
Research on p-type amorphous semiconductors has been noticeably slow. Many intrinsic defects have hampered the development of p-type oxide materials, even though n-type amorphous oxide semiconductors—especially those based on indium gallium zinc oxide (IGZO)—have been widely used in OLED displays and memory devices. This setback has impeded the advancement of complementary bipolar semiconductors (CMOS), n-p-type, the building block of integrated circuits and electronic devices.
After two decades of fruitless attempts, academia has long been faced with the challenge of creating high-performance amorphous p-type oxide semiconductor devices.
Nevertheless, the seemingly "impossible" has been made "possible" by a group of researchers led by POSTECH Professor Yong-Young Noh.
The team’s research revealed that tellurium oxide, a rare earth metal, has a higher charge in environments with low oxygen levels. This phenomenon results from the material’s ability to function as a p-type semiconductor due to the formation of an acceptor level that can hold electrons in the absence of enough oxygen.
Using partially oxidized tellurium thin films and a tellurium-selenium composite oxide (Se:TeOx) incorporating selenium, the team successfully engineered high-performance and exceptionally stable amorphous p-type oxide Thin-Film Transistors (TFTs).
According to experimental results, the team's TFTs have the greatest hole mobility (15 cm2V-1s-1) and on/off current ratio (106-107) for a p-type amorphous oxide TFT ever documented. These accomplishments almost match the performance levels of well-researched conventional n-type oxide semiconductors (like IGZOs).
The team's TFTs also showed remarkable stability in a range of external circumstances, such as variations in humidity, air quality, voltage, and current. Notably, when TFT components were fabricated on wafers, consistent performance was seen across all of them, confirming their suitability for dependable semiconductor devices used in industrial settings.
This milestone holds significant implications for next-generation display technologies such as OLED TVs, VR, and AR devices, as well as for research on low-power CMOS and DRAM memory. We anticipate its potential to drive substantial value creation across diverse industries.
Yong-Young Noh, Professor, Pohang University of Science and Technology
Samsung Display, the National Research Foundation of Korea's Mid-Career Researcher Program, and the National Semiconductor Laboratory Program funded the study.
Journal Reference:
Liu, A., et al. (2024) Selenium alloyed tellurium oxide for amorphous p-channel transistors. Nature. doi.org/10.1038/s41586-024-07360-w