Impact of pixel scaling and dual-layer passivation on the electro-optical characteristics of AlGaInP-based red µ-RCLEDs for high-speed optical communication

• Reducing the dimensions of micro-scale resonant-cavity light-emitting diodes enhances optical confinement and improves emission stability, enabling faster and more efficient operation for visible-light communication. • Introducing a dual-layer silicon dioxide and aluminum oxide passivation suppresses sidewall defects and strengthens carrier confinement at the device periphery, thereby improving the stability and efficiency of the emitted light. • Devices incorporating dual-layer passivation deliver higher light output, improved emission efficiency, and enhanced high frequency response, demonstrating the synergistic benefit of geometric scaling and interface engineering. • The optimized structures maintain stable emission spectra with minimal linewidth variation and provide improved emission directionality, effectively mitigating efficiency degradation during miniaturization. The influence of pixel scaling and dual-layer surface passivation on the electro-optical characteristics of AlGaInP-based red-emitting micro-resonant cavity light-emitting diode (µ-RCLED) was systematically examined. Circular pixels with diameters of 50 μm, 25 μm, and 10 μm were integrated within a constant 50 × 50 μm² footprint to isolate geometric confinement effects on carrier transport, radiative efficiency, and high-frequency response. Devices employing single-layer silicon dioxide (SiO 2 ) exhibited light-output powers of 2.51, 1.76, and 0.55 mW and external quantum efficiencies of 8.45%, 5.91%, and 1.84%, accompanied by leakage current increases of 242% and 236% for the 25 μm and 10 μm arrays as the sidewall to volume ratio intensified. The implementation of a dual-layer SiO 2 /Al 2 O 3 passivation architecture leads to an effective suppression of sidewall-related defect states, thereby mitigating nonradiative recombination losses. This structural modification is accompanied by light output power enhancements of 15.5%, 8.5%, and 36.4%, together with corresponding external quantum efficiency improvements of 15.3%, 8.5%, and 37% relative to devices employing single-layer passivation. Frequency domain measurements further revealed bandwidth expansion from approximately 100 MHz to 260 MHz, corresponding to enhancements of 126%, 162%, and 210% with decreasing pixel size. These findings establish a direct linkage between geometric scaling, interfacial defect control, and performance optimization, highlighting the efficacy of dual-layer passivation in enabling high-efficiency, high-bandwidth µ-RCLED for visible-light communication.