Researchers from Taiwan’s National Chiao Tung University, China’s Xiamen University and SIJ Technology have developed a monolithic Micro LED which achieves full-color display. The study demonstrates that Micro LED full-color display can be realized without mass transferring and the result was published on Scientific Reports and Photonics Research.

The team fabricated the Micro LED full-color display on monolithic epitaxial wafer by combining nanoring (NR) structure and atomic layer deposition. From previous study, the researchers have demonstrated a wavelength tunable nanoring Micro LED (NR Micro LED) by strain-induced engineering, showing that the green NR Micro LED can be tuned to blue via controlling the wall width.

The new development noted that nanoring structure would erode part of the lighting area and reduce external quantum efficiency. The small size of Micro LED makes it easier to be impacted by the sidewall damage. The research team aimed to improve the lower external quantum efficiency via the implement of atomic layer deposition (ALD).

A hybrid quantum dot nanoring Micro LED (QD-NR Micro LED) is then proposed by the research. The device is composed of three parts, a normal green LED, a blue NR Micro LED, and a red QD-NR Miro LED. The red LED is achieved by printing red QDs on the blue NR Micro LED to achieve full color display.

Through the adoption of ALD, the thin layer between multiple quantum wells and quantum dots of NR Micro LED can be controlled and nonradiative resonant energy transfer (NRET) for color conversion can be maintained.

(Image: NCTU/Photonics Research)

With the study, the team developed full-color Micro LED that its lighting efficiency is improved with atomic layer deposition and QD color transfer efficiency is enhanced via nonradiative resonant energy transfer. The approach provides a new insight for Micro LED full-color realization.