Suppressing sidewall photon leakage in ultra-small Micro-LEDs via omnidirectional reflector integration

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Micrometer-scale Micro-LEDs face challenges with conventional reflectors like distributed Bragg reflectors (DBRs) due to performance degradation under varying conditions.
• Light extraction efficiency is limited in small GaN-based Micro-LEDs by sidewall thickness variations and oblique photon incidence.

Purpose of the Study:

• To investigate the integration of omnidirectional reflectors (ODRs) into GaN-based Micro-LEDs.
• To enhance photon management and external quantum efficiency (EQE) in ultra-small Micro-LED devices.

Main Methods:

• Simulations were used to evaluate ODR performance under sidewall thickness variation and wide-angle incidence.
• Experimental integration of ODRs into 2 μm lateral size GaN-based Micro-LEDs.

Main Results:

• ODRs demonstrated maintained high reflectance under varying sidewall thickness and wide-angle incidence, unlike DBRs.
• Micro-LEDs with ODRs achieved a peak EQE of 42.3%, a significant increase from 25.6% without an optical reflector.
• ODR integration resulted in a 67% relative improvement in EQE and maintained stable electrical characteristics across a broad current density range.

Conclusions:

• ODR integration is a scalable and practical strategy for improving photon extraction in ultra-small GaN-based Micro-LEDs.
• The enhanced photon management and EQE have direct implications for the development of high-resolution micro-display applications.