# High efficiency, high color purity red micro-light-emitting diodes

## TL;DR

Researchers developed red micro-LEDs with high efficiency and color purity using a nanowire photonic crystal structure, addressing key challenges in red emission for display and lighting technologies.

## Contribution

A nanowire photonic crystal structure is introduced to achieve high-efficiency, high-color-purity red micro-LEDs with narrow emission and stable chromaticity.

## Key findings

- Red micro-LEDs achieved a peak wavelength of 617 nm with a FWHM of 5 nm, significantly narrower than previous reports.
- The devices exhibited high external quantum efficiency of over 10% for 1 µm² micro-LEDs.
- Chromaticity remained stable across varying injection currents due to photonic band edge mode coupling.

## Abstract

InGaN-based micro-light-emitting diodes (micro-LEDs) are emerging to revolutionize the display and lighting technologies, particularly for their excellent robustness, high brightness, high efficiency and small pixel size. Despite the success of blue LEDs, long-wavelength emission, particularly the red emission, has been a challenge for InGaN-based micro-LEDs. Overcoming the low quantum efficiency, color instability, and broad emission in the red wavelength regime are among the most urgent and critical problems that inhibit the commercial implementation of micro-LED technology. In this work, we utilize a nanowire photonic crystal (PhC) structure to reform the radiation behavior of red-emitting InGaN micro-LEDs. Through detailed optimization on the PhC design and device fabrication, we demonstrate red-emitting micro-LEDs with a peak wavelength at 617 nm and a full-width-at-half-maximum (FWHM) of 5 nm, which is about one order of magnitude narrower than previous reported values and is paramount for achieving high color purity. The chromaticity property is highly stable with varying injection currents due to the coupling of emission to photonic band edge mode. A high external quantum efficiency of over 10% was measured from micro-LEDs with a size of 1 µm2. This work provides a vital strategy for high-performance red-emitting micro-LEDs and a potential pathway for full-color micro-LED technology by using all III-nitride semiconductors.