In the relentless pursuit of smaller, faster, and more efficient electronic devices, researchers have long been challenged by the degradation of performance in ultra-thin semiconductor materials. A recent study led by JinKyu Lee from the Department of Electrical and Computer Engineering at Seoul National University has shed light on a promising solution to this persistent issue, with significant implications for the energy sector and beyond.
The study, published in the journal *Applied Surface Science Advances* (translated as *Advances in Surface Science and Technology*), focuses on amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs), a material widely used in displays and other electronic applications. As devices become increasingly compact, the channel thickness of these TFTs is reduced to just a few nanometers. However, this reduction brings about a significant decrease in mobility and current crowding, severely limiting the performance of the devices.
Lee and his team discovered that this degradation is primarily caused by titanium (Ti)-induced oxidation and trap formation, which extend into the IGZO channel bulk. “When the channel thickness is reduced below 5 nm, we observed a dramatic decrease in field-effect mobility to approximately 0.2 cm²/V·s,” Lee explained. “This is a critical bottleneck for the development of next-generation electronic devices.”
To address this issue, the researchers introduced an atomic-layer-deposited (ALD) aluminum oxide (Al₂O₃) interlayer (IL) at the Ti/IGZO interface. Despite the strong reactivity of the trimethylaluminum (TMA) precursor used in ALD with IGZO components, the self-limiting surface reaction characteristic of ALD confines chemical interactions to the IGZO surface. This forms a uniform and dense dielectric film without damaging the underlying channel.
The resulting Al₂O₃ layer acts as a thermodynamically stable diffusion barrier, preventing spontaneous redox reactions with Ti and effectively suppressing the formation of interfacial oxides. “The Al₂O₃ IL preserves the chemical and structural integrity of the IGZO channel and enables robust electron injection at the contact interface,” Lee noted. With a 3 nm-thick IL, the field-effect mobility of ultra-thin 3 nm IGZO TFTs was significantly enhanced from ∼0.2 to ∼2.4 cm²/V·s.
The implications of this research are far-reaching, particularly for the energy sector. High-performance TFTs are crucial for the development of energy-efficient displays and sensors, which are essential for smart grids and renewable energy systems. By mitigating electrical degradation in ultra-thin IGZO TFTs, this study paves the way for more efficient and compact electronic devices, ultimately contributing to a more sustainable energy future.
As the demand for smaller and more powerful electronic devices continues to grow, the need for innovative solutions to performance degradation becomes ever more pressing. Lee’s research highlights the importance of interfacial engineering in addressing contact resistance issues in ultra-thin oxide semiconductors. “This study provides a scalable and effective strategy for developing high-performance IGZO-based TFTs for next-generation electronic applications,” Lee concluded.
With the findings published in *Applied Surface Science Advances*, the scientific community now has a clearer path forward in the quest for advanced semiconductor materials. As researchers and engineers continue to build upon this work, the potential for breakthroughs in the energy sector and beyond becomes increasingly promising.