High-efficiency InGaN/GaN red micro-LEDs using nanoporous GaN compliant buffer for stress relaxation and light extraction enhancement

초록

GaN-based micro-light-emitting diodes (micro-LEDs) have attracted significant interest in visible-light applications, however, their external quantum efficiency (EQE) remains severely limited by crystalline defects and strain in the active region. This is particularly critical for red micro-LEDs, where high indium incorporation and low growth temperatures induce significant internal stress and a pronounced quantum-confined Stark effect (QCSE). To address these challenges, we introduce a nanoporous GaN structure fabricated via sequential electrochemical (EC) and electrochemical-photoelectrochemical (EC-PEC) etching as a compliant buffer layer. The red LEDs regrown on EC-PEC nanoporous GaN with a porosity of 20% exhibit a 56% reduction in biaxial stress (sigma LED) and a 36% decrease in threading dislocation density. The effective stress relaxation enhances indium incorporation in the InGaN active layer and reduces the internal electric field, resulting in a red-shifted electroluminescence peak and suppressed QCSE. Consequently, 50 & times; 50 mu m2 red micro-LEDs demonstrate a 22.4% enhancement in maximum EQE, along with increased light output. These results confirm that nanoporous GaN enables simultaneous improvements in crystalline quality, internal quantum efficiency and light extraction efficiency. The EC-PEC nanoporous GaN platform provides an effective strategy for mitigating efficiency degradation in long-wavelength InGaN micro-LEDs and offers a promising pathway toward high-efficiency micro-display applications.

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