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

Ultrasmall blue InGaN micro-light-emitting diodes (mu LEDs) with areas from 10(-4) to 0.01mm(2) were fabricated to study their optical and electrical properties. The peak external quantum efficiencies (EQEs) of the smallest and largest mu LEDs 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 AllnGaP LEDs. The efficiency droop at 900 A/cm(2) of the smallest mu LED was 45.7%, compared with 56.0% for the largest, and was lower because of improved current spreading. These results show that ultrasmall mu LEDs may be fabricated without a significant loss in optical or electrical performance. (C) 2017 The Japan Society of Applied Physics