A domestic research team has developed a new semiconductor material structure that efficiently emits light in the deep ultraviolet range, long considered extremely difficult to achieve with existing semiconductor technology. Deep ultraviolet refers to the portion of ultraviolet light with particularly short wavelengths of 200–280 nm (nanometers, one-billionth of a meter).
The Ministry of Science and ICT said on the 20th that a research team led by Kim Jong-hwan of Pohang University of Science and Technology POSTECH and Director General Cho Moon-ho of the Institute for Basic Science (IBS) significantly boosted deep ultraviolet emission efficiency by implementing a new type of "quantum well" structure based on van der Waals semiconductors. The team said emission efficiency improved more than 20 times compared with conventional aluminum gallium nitride materials. The findings were published in Science on the 20th.
Semiconductor light source technology has so far advanced mainly in the visible light range that people can see with the naked eye. Light-emitting diode (LED) lighting, displays, and lasers are representative examples. Recently, development has expanded into the ultraviolet range with shorter wavelengths. In particular, after the COVID-19 pandemic, interest has grown in deep ultraviolet light sources that can be used to eliminate bacteria and viruses.
The problem is efficiency. Current ultraviolet LEDs are mainly made on gallium nitride–based semiconductors. Mixing in aluminum to make aluminum gallium nitride allows emission of even shorter wavelengths. However, as the wavelength shortens to around 200–240 nm, efficiency drops sharply. In this range, light source efficiency often falls below 1%, making it one of the most technically challenging areas.
To overcome this limit, the researchers chose to change the structure itself. They used boron nitride (BN), which has a "van der Waals layered structure." In van der Waals materials, atoms are strongly bonded within a layer but are relatively weakly attached between layers, making it easy to peel them thin or stack them at different angles.
The team noted that when boron nitride layers are stacked with a slight twist, a special structure forms that confines electrons in an extremely narrow space. The researchers called this structure a "moiré quantum well."
Here, a quantum well refers to a structure that confines particles such as electrons in a very small space to create specific energy states. It is a concept often used to control the wavelength or efficiency of light in semiconductor devices. "Moiré" describes the phenomenon in which a new large pattern appears when two patterns are overlapped with a slight offset, and something similar happens in atomic layers. In other words, slightly twisting stacked atomic layers changes how electrons move, enabling the creation of light with properties different from before.
The significance of this study is not just that it improved efficiency. Research on quantum phenomena in van der Waals materials has mainly focused on ultrathin two-dimensional films like graphene. This time, however, the team showed that a distinctive two-dimensional quantum well structure can be created by the relatively simple approach of twisting and stacking boron nitride in a three-dimensional crystal form.
Meanwhile, because of its strong sterilizing effect, deep ultraviolet has drawn attention for use in multiuse facilities such as hospitals, schools, and public transportation. However, ultraviolet light around 260 nm that is often discussed today can harm human skin or eyes, limiting its use. In contrast, the so-called "shorter-wavelength deep ultraviolet" in the 200–230 nm band has been studied as a wavelength range that may be relatively safe because it does not penetrate deeply into the outer layer of the skin.
This achievement is meaningful in that it offers a clue to solving the low emission efficiency problem that has been the biggest obstacle precisely in the 200–230 nm range. If a high-efficiency light source leads to an actual device, it could be connected to next-generation hygiene technology that continuously manages air or surfaces in crowded indoor spaces.
Kim Jong-hwan said, "This is a conceptual shift that extends the unique moiré quantum physics observed in van der Waals materials from two-dimensional to three-dimensional materials," adding, "This research will serve as a starting point for designing new quantum materials and developing next-generation optoelectronic devices."
References
Science (2026) DOI: https://doi.org/10.1126/science.aeb2095