Professor resolves two decades of oxide semiconductor challenges

This innovative material has been used to create a highly stable and high-performance p-type thin-film transistor (TFT). The research findings were recently published online in Nature.

Overview of the semiconductor types

Semiconductors are integral to a wide array of electronic devices, from mobile phones and PCs to cars. They are broadly categorised into two types: crystalline and amorphous. Crystalline semiconductors are known for their well-ordered atomic structures, while amorphous semiconductors, though cheaper and simpler to produce, generally lag behind in electrical performance.

Challenges and innovations in amorphous semiconductors

The development of p-type amorphous oxide semiconductors has been relatively slow compared to their n-type counterparts, which are prominently used in devices like OLED displays and memory devices. The challenge in enhancing p-type materials has primarily stemmed from their inherent defects, which have historically stymied the advancement of complementary bipolar semiconductors (CMOS) essential for electronics and integrated circuits.

The research breakthrough

Professor Noh's team made a discovery that the charge of tellurium oxide increases in oxygen-deficient environments, due to the creation of an acceptor level that can accommodate electrons. This finding led to the successful development of high-performance and remarkably stable amorphous p-type oxide TFTs. These were engineered using partially oxidised tellurium thin films and a selenium-enhanced tellurium oxide (Se:TeOx).

The TFTs developed by the POSTECH team have demonstrated unprecedented hole mobility (15 cm²V⁻¹s⁻¹) and on/off current ratios (10⁶-10⁷), rivalling the performance of conventional n-type oxide semiconductors. Furthermore, these TFTs exhibited exceptional stability under various external conditions, such as voltage and humidity fluctuations, showcasing uniform performance when fabricated on wafers. This ensures their reliability for industrial use.

Professor Yong-Young Noh commented on the implications of this research, stating: “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.” He also noted the potential for this technology to drive value creation across multiple industries.

This research was supported by the National Semiconductor Laboratory Program and the Mid-Career Researcher Program of the National Research Foundation of Korea, along with Samsung Display.