Spectrally\nPure, High Operational Dynamic Range, Deep\nRed Micro-LEDs

III-nitride-based micro-light-emitting diodes (micro-LEDs)\nare\ncurrently under rapid development for next-generation high-resolution\nand high-brightness displays and augmented/virtual reality (AR/VR)\ntechnologies. However, it remains elusive to achieve red-emitting\nIII-nitride micro-LEDs with a microscale size, high efficiency, and\nhigh spectral stability, posing significant impediments to the development\nof full-color micro-LEDs. In this work, through detailed strain engineering\nand control of charge carrier transport, we achieved pure red emission\n(≥620 nm) micro-LEDs over 2 orders of magnitude of injection\ncurrent variation. We show both theoretically and experimentally that\nthe combination of a short-period InGaN/GaN superlattice and a thick\nn-type GaN interlayer can not only relieve the quantum-confined Stark\neffect in the active region but also suppress parasitic emission from\nthe superlattice. The optimized deep red micro-LEDs with a device\nlateral dimension of ∼1 μm feature a maximal external\nquantum efficiency of over 3% emitting at ∼660 nm.