Enhanced Emission and Polarization Control of Green GaN-Based Resonant Cavity LEDs with Porous Distributed Bragg Reflectors

Green InGaN-based resonant-cavity light-emitting diodes (RC-LEDs) with integrated nanoporous (NP) GaN distributed Bragg reflectors (DBRs) were fabricated by using a selective electrochemical (EC) etching technique. The epitaxial structure comprised 25 alternating Si-doped GaN layers, forming a periodic high- and low-refractive-index stack after the EC etching process. The resulting porous-GaN DBR exhibited an effective refractive index of 2.02 and a stopband centered at 566 nm, achieving 98% reflectivity. By integrating a top-3-pairs dielectric mirror, the electroluminescence (EL) spectra showed a narrower full width at half-maximum (fwhm) from 41 nm (nontreated LED) to 12.8 nm (RC-LED). Polarization analysis revealed two spectral peaks at 536.7 and 544.7 nm, with one suppressed by a polarizer. The fwhm varied with the polarization direction, being 5.2 nm at 0° and 6.4 nm at 90°. These results demonstrate that integrating bottom porous GaN and top dielectric DBRs yields a high-reflectivity, low-loss RC structure suitable for high light coupling in fiber interconnection and high-color-purity micro-LED display applications.