Achieved Lossless Exciton Control at Last... UNIST Develops 'World's First' Technology

Momentum Grows in Semiconductor and Optical Communication Device Development

Professor Kyungduk Park's team in the Department of Physics at Ulsan National Institute of Science and Technology (UNIST) has developed the world's first technology to control exciton particles without loss. The photo shows Professor Kyungduk Park (far left), co-first authors Hyungwoo Lee (front row, left), and Yeonjeong Koo (right). Photo by Kyungduk Park

[Asia Economy Yeongnam Reporting Headquarters Reporter Lee Seryeong] Professor Park Kyung-deok's team from the Department of Physics at Ulsan National Institute of Science and Technology (UNIST) announced that they have developed the world's first technology to control exciton particles (quasiparticles) without loss.

An exciton is a particle formed inside insulating or semiconductor materials, consisting of a negatively charged electron (-) and a positively charged hole (+), making it electrically neutral.

As more elements are integrated to enhance chip performance, unwanted electric field interference occurs, but neutral excitons do not cause interference even when elements are densely integrated. Using excitons instead of electrons can create semiconductor chips that operate faster and generate no heat.

An experimental confirmation of high-efficiency exciton behavior.

To create exciton-based semiconductor chips, a mechanical deformation method that bends the semiconductor material is used, but exciton particles can easily be lost during this process.

If bent too strongly, the material itself can be permanently damaged, and if the deformation is insufficient, exciton particles inside the material disappear due to external factors such as heat.

Professor Park Kyung-deok's team, which developed technology to freely and efficiently control excitons, stated that this technology will accelerate the development of next-generation semiconductor chips.

Since exciton particles emit light when electrons and holes bound by electrostatic force combine, there is no need to convert digital information into separate optical signals, making it advantageous for ultra-high-speed optical communication development.

In this study, the research team created a device with a nano-gap structure to overcome the limitations of excitons that are easily lost during deformation.

The device consists of a thin two-dimensional semiconductor material stretched over the gap structure, with the material rolled into the gap.

The length of the gap is very short, on the order of hundreds of nanometers (nm, one billionth of a meter), which helps reduce losses.

An illustration depicting the observation of nanoscale exciton behavior using a tip-enhanced photoluminescence nanoscope.

To reduce exciton loss, a high strain?defined as the deformation per unit length of the two-dimensional semiconductor material?is required, and the research team solved this by utilizing the tip of a previously developed ‘active probe-enhanced photoluminescence nanoscope’.

By pressing the two-dimensional semiconductor material with the microscope tip, the behavior of exciton particles generated inside the material can be controlled more efficiently.

The tip of the active probe-enhanced photoluminescence nanoscope is about 10 nm in cross-sectional area, allowing the pressure applied per unit area of the two-dimensional semiconductor material to reach gigapascal (GPa) levels.

The higher the pressure applied, the greater the strain, and when the probe is removed, the mechanical deformation returns to its original state, which is another advantage of this technology.

The research was led by graduate students Lee Hyung-woo and Koo Yeon-jung from the Department of Physics. The nano-gap devices used in the study were fabricated by the research teams of Vice President Joo Hyuk at Samsung Electronics and Professor Park Hyung-ryul at UNIST’s Department of Physics, while Professor Kim Ki-gang’s team from Sungkyunkwan University’s Department of Energy Science participated in producing the two-dimensional semiconductor materials.

The research results were published on February 4 in the international journal Science Advances, and the research was supported by the National Research Foundation of Korea, UNIST, and the Institute for Basic Science (IBS).

The research team stated, “We have identified exciton behavior phenomena at the nanoscale for the first time in the world and found a solution to the efficiency problem, which was a limitation of previous exciton behavior control studies,” adding, “This is a new study that breaks the conventional wisdom of existing exciton behavior control research.”

Professor Park Kyung-deok said, “The exciton-based device introduced this time is a dynamic device that can be freely controlled,” and added, “It can also be used for the development and performance improvement of various exciton-based nano semiconductors and optical communication devices.”

This content was produced with the assistance of AI translation services.