High external quantum efficiency in ultra-small amber InGaN microLEDs scaled to 1 μm

Micro-light-emitting diodes (microLEDs) can improve existing displays and enable disruptive technologies like augmented reality (AR). However, ignoring smaller devices near 1 μm overlooks (at least) two additional size-dependent effects that improve microLED efficiency: directionality and extraction efficiency increase as size decreases, and surface recombination is reduced as indium content increases (in InGaN microLEDs). This study shows that both combined effects counteract size-dependency efficiency droop, where the magnitude of positive effects increases with indium concentration (from blue to red) in InGaN. As the microLEDs' diameter reduced from 50 to 1 μm, the external quantum efficiency (EQE) of 500 nm microLEDs fell from 16.5% to 14%, while the EQE of 600 nm devices increased from 2.7% to 7.1%. Although the efficiency of conventionally sized AlInGaP LEDs remains significantly higher than InGaN, the results of this study suggest that very high EQE of red microLED with sizes approaching 1 μm can be realized using InGaN materials instead of AlInGaP. In addition to improving performance, consolidating to an entirely InGaN-based microLED display would reduce costs and streamline resources to help achieve AR and other next-generation displays.