Strain-engineered N-polar InGaN nanowires:towards high-efficiency red LEDs on the micrometer scale

The absence of efficient red-emitting micrometer-scale light emitting diodes(LEDs),i.e.,LEDs with lateral dimensions of 1μm or less is a major barrier to the adoption of microLEDs in virtual/augmented reality.The underlying challenges include the presence of extensive defects and dislocations for indium-rich InGaN quantum wells,strain-induced quantum-confined Stark effect,and etch-induced surface damage during the fabrication of quantum well microLEDs.Here,we demonstrate a new approach to achieve strong red emission(>620 nm)from dislocation-free N-polar InGaN/GaN nanowires that included an InGaN/GaN short-period superlattice underneath the active region to relax strain and incorporate more indium within the InGaN dot active region.The resulting submicrometer-scale devices show red electroluminescence dominantly from an InGaN dot active region at low-to-moderate injection currents.A peak external quantum efficiency and a wall-plug efficiency of 2.2%and1.7%were measured,respectively,which,to the best of our knowledge,are the highest values reported for a submicrometer-scale red LED.This study offers a new path to overcome the efficiency bottleneck of red-emitting microLEDs for a broad range of applications including mobile displays,wearable electronics,biomedical sensing,ultrahigh speed optical interconnect,and virtual/augmented reality.