A research team led by Professor Park Kyung-deok of the departments of physics and semiconductor engineering and the graduate schools of convergence and semiconductors at Pohang University of Science and Technology POSTECH said on the 4th it developed an optical data storage technology that can store hundreds of thousands of times more information than existing methods.
The file size of a single smartphone photo is more than 10 times larger than 10 years ago. Ultra-high-definition video is even heavier. On top of that, as artificial intelligence (AI) services spread, the data generated and processed is also increasing, and demand for storage space is rising exponentially.
To store growing amounts of information, more storage slots must be created. However, shrinking the size of each slot to do so runs into electrical interference and physical limits. In particular, optical storage technology that uses light has struggled to raise integration density to the nanometer (nm, one-billionth of a meter) scale because light tends to spread.
The research team focused on excitons, particles formed when light and electrons couple inside a semiconductor. An exciton is a particle that has the properties of both light and electrons, and by precisely controlling the state of this particle, multiple levels of information can be expressed in a single storage cell. Just as a traffic signal sends different signals depending on whether it is red, yellow, or green, the team devised a method of dividing exciton emission brightness into multiple levels to store two or more pieces of information in one cell.
To achieve this, the team built a nano tunnel junction device by stacking a metal–insulator–semiconductor structure. In this structure, fine-tuning charge transport transforms excitons into another particle state, changing the intensity of light. Using this, the team succeeded in implementing three or more emission states in a single cell about 60 nm in size. They also thinned the storage layer to 15 nm or less (about 1/5,000 the thickness of a human hair), laying the groundwork to stack devices more densely.
The technology developed this time can read and write data in a non-contact manner using light, reducing wear and damage to devices. Lee Hyeong-woo, the first author of the paper, said, "While existing technology relied on expanding storage space, this study is significant in that it used the state of excitons inside a semiconductor itself, rather than light intensity, as the unit of information," and added, "If applied in various fields such as data centers and AI servers, next-generation semiconductor memory, and smart devices, it could become a turning point that changes the paradigm of storage technology."
The study was published in December last year in ACS Nano, an international journal in nanoscience, and was selected as the cover article.
References
ACS Nano (2025), DOI: https://doi.org/10.1021/acsnano.5c15152