Sustained high external quantum efficiency in ultrasmall blue III-nitride micro-LEDs

Ultrasmall blue InGaN micro-light-emitting diodes (µLEDs) with areas from 10−4 to 0.01 mm2 were fabricated to study their optical and electrical properties. The peak external quantum efficiencies (EQEs) of the smallest and largest µLEDs were 40.2 and 48.6%, respectively. The difference in EQE was from nonradiative recombination originating from etching damage. This decrease is less severe than that in red AlInGaP LEDs. The efficiency droop at 900 A/cm2 of the smallest µLED was 45.7%, compared with 56.0% for the largest, and was lower because of improved current spreading. These results show that ultrasmall µLEDs may be fabricated without a significant loss in optical or electrical performance.