KAIST

<(Back row, from left) Dr. Juhyuk Park, Ph.D candidate Hyunsu Ki, (Front row, from left) M.S candidate Haoi Le Bao, M.S candidate Chaeyeon Kim, (Circled, from left) Prof. Sanghyeon Kim, Prof. Dae-Myeong Keum >

From TVs and smartwatches to rapidly emerging VR and AR devices, micro-LEDs are a next-generation display technology in which each LED—smaller than the thickness of a human hair—emits light on its own. Among the three primary colors required for full-color displays—red, green, and blue—the realization of high-performance red micro-LEDs has long been considered the most difficult. KAIST researchers have now successfully demonstrated a high-efficiency, ultra-high-resolution red micro-LED display, paving the way for displays that can deliver visuals even sharper than reality.

KAIST (President Kwang Hyung Lee) announced on the 28th that a research team led by Professor Sanghyeon Kim of the School of Electrical Engineering, in collaboration with Professor Dae-Myeong Geum of Inha University, compound-semiconductor manufacturer QSI, and microdisplay/SoC design company Raontech, has developed a red micro-LED display technology that achieves ultra-high resolution while significantly reducing power consumption.

Using this technology, the team successfully demonstrated a 1,700 PPI* class ultra-high-resolution micro-LED display—approximately 3–4 times higher than the resolution of current flagship smartphone displays—capable of delivering truly “reality-like” visuals even in VR and AR devices.
 *PPI (Pixels Per Inch): indicates how densely pixels are packed on a display; higher PPI corresponds to finer image detail.

Micro-LEDs are self-emissive displays that surpass OLEDs in brightness, lifetime, and energy efficiency, but they have faced two major technical challenges. The first is the efficiency degradation of red micro-LEDs, which becomes severe as pixel sizes shrink due to increased energy leakage. The second is the limitation of conventional transfer processes, which rely on mechanically locating and placing countless microscopic LEDs one by one, making ultra-high-resolution fabrication difficult and increasing defect rates.

<Results of Red Micro-LED Performance Improvement>

The research team addressed both challenges simultaneously. First, they adopted an AlInP/GaInP quantum-well structure, enabling highly efficient red micro-LEDs with minimal energy loss even at very small pixel sizes. Simply put, the quantum well/barrier structure acts as an “energy barrier.” It confines electrons and holes within the quantum well layer, preventing carrier leakage. By adopting quantum wells with higher hole concentration, the research team effectively reduced energy loss as pixel sizes decreased, enabling brighter and more efficient red micro-LEDs.

Also, instead of transferring individual LEDs, the researchers employed a monolithic three-dimensional (3D) integration technique, stacking the LED layers directly on top of the driving circuitry. This approach minimizes alignment errors, reduces defect rates, and enables stable fabrication of ultra-high-resolution displays. The team also developed a low-temperature process to prevent damage to the underlying circuitry during integration.

<Monolithic 3D MicroLED-on-Si Display>

This achievement is particularly significant because it demonstrates a fully functional, ultra-high-resolution, and highly-quantum-efficient red micro-LED display, widely regarded as the most difficult component to realize. The technology is expected to find broad applications in next-generation displays where pixel granularity must be virtually imperceptible, including AR/VR smart glasses, automotive head-up displays (HUDs), and ultra-compact wearable devices.

Professor Sanghyeon Kim commented, “This work simultaneously solves the long-standing challenges of red pixel efficiency and circuit integration in micro-LEDs. We will continue to advance this technology toward practical commercialization as a next-generation display platform.”

The study was led by Dr. Juhyuk Park of the KAIST Institute of Information Electronics as first author, and the results were published on January 20 in the international journal Nature Electronics.
 ※ Paper title: “A Monolithic Three-Dimensional Integrated Red Micro-LED Display on Silicon Using AlInP/GaInP Epilayers”
 ※ DOI: 10.1038/s41928-025-01546-4

This research was supported by the National Research Foundation of Korea Basic Research Program (2019), the Display Strategic Research Laboratory Program (currently ongoing), and the Samsung Future Technology Incubation Center (2020-2023).

<Monolithic 3D Direct Technology (AI-generated image)>