Dual-Chemical Etching Strategy for Extended-Depth Macroporous GaN: Realizing Pure Quantum Dot Emission for Color-Conversion Applications

Quantum dot (QD)-integrated microlight-emitting diodes (μ-LEDs) have emerged as a promising technology for full-color displays; however, they face a critical challenge in achieving high color purity owing to the leakage of blue excitation light. This leakage mixes with the converted emission, leading to severe optical crosstalk and a degraded color gamut. While porous GaN is a promising solution, the scattering medium formation via electrochemical etching is confined to an n-type GaN layer. However, this structure requires a thick n-GaN layer to completely suppress the blue excitation light. To address this limitation, we have developed a dual-chemical treatment strategy that extends the porous structure to the underlying undoped GaN (u-GaN) layer. First, we optimized the single-step etching process, identifying a medium-doped template (Nd = 6 × 1018 cm–3) as the best scattering medium. Next, an ultraviolet-assisted photoelectrochemical treatment expanded the porous region into the u-GaN layer and increased the porosity to 75%, transforming the morphology into a macroporous structure. This structural evolution achieved a near-unity QD emission ratio of 99.8% with a 37.7-fold reduction in light leakage, offering a viable route toward high-performance, full-color μ-LED displays.