Optimizing Al Composition in Barriers for InGaN Amber Micro-LEDs With High Wall-Plug Efficiency

This study demonstrated InGaN-based amber micro-light-emitting diodes ( $\mu $ LEDs) with varying Al contents of 2%, 5%, and 16% in barriers. The $\mu $ LEDs with Al $_{\mathbf {{0}.{05}}}$ GaN in barriers exhibited the highest on-wafer wall-plug efficiency due to the good material quality and optimal energy band engineering for carrier injection. We fabricated $\mu $ LEDs with diameters ranging from 60 to $10~\mu \text{m}$ using the optimal epi-structure. The forward voltage was 2.15 V at 1 A/cm $^{\mathbf {{2}}}$ , a significantly lower value compared to others. The external quantum efficiency and wall-plug efficiency of the packaged $\mu $ LEDs with a diameter of $10 ~\mu \text{m}$ are 4.8% and 4% at 1 A/cm $^{\mathbf {{2}}}$ , respectively. The slight decrease in efficiency of 10- $\mu \text{m} \mu $ LEDs can be attributed to the sidewall effect, which was confirmed by photoluminescent and lifetime mapping.