Korean researchers develop technology to overcome resolution limitations of micro LED displays

A team of Korean researchers has come up with technology that can overcome the resolution limitations of micro LED displays, which are attracting much attention as a next-generation display. The new technology is expected to be used to produce high-resolution small displays for virtual reality (VR) and augmented reality (AR) applications.

The Korea Advanced Institute of Science and Technology (KAIST) announced on Jan. 6 that a research team led by Prof. Kim Sang-hyun at the Department of Electrical and Electronics Engineering has developed technology to produce more than 63,500 pixels per inch (PPI) using semiconductor fabrication technology.

Micro LED displays use micrometer-sized inorganic LEDs as pixels. To use inorganic LEDs as pixels, red, green, and blue (RGB) pixels must be closely arranged, but LED materials that can produce the three colors are different from each other. So each LED must be transcribed on a display substrate.

In this process, many technical difficulties arise, such as the limits in the size of an LED transfer head and mechanical accuracy, and a reduction in yields, making it difficult to apply the technology to ultra-high resolution displays.

The research team has developed a new method to produce devices for ultra-high resolution micro LED displays. They use a semiconductor patterning process after stacking red, green and blue LED active layers in three dimensions. To solve the problems such as color interference that arises when LEDs are stacked vertically and the efficiency of tiny pixels, the team removed 97 percent of red and blue interference light by putting an insulating film with characteristics of a filter on a joining surface. The team achieved a resolution of over 60,000 PPI in this way and improved the efficiency of tiny LEDs.