Fig. 1. Process flow for the fabrication of a full-color RGB pixel array. (a) μ-LED array process. (b) Black PR matrices and p-electrode metal lines. (c) Red, green, and blue (transparent) pixel lithography process. (d) Color pixel bonding.

Fig. 2. (a) Schematic diagram of the semipolar GaN grown on a patterned sapphire substrate. (b) Photograph of a 4 in. wafer of SF-free (20-21) InGaN/GaN LED grown on a patterned sapphire substrate. (c) Top-view microscopy image of SF-free (20-21) InGaN/GaN LED grown on a patterned sapphire substrate. (d) Cross-sectional SEM image of (20-21) GaN grown on a patterned sapphire substrate by orientation-controlled epitaxy.

Fig. 3. (a) J-V curve of semipolar μ-LEDs, with image of lighting from device. (b) Electroluminescence spectrum of semipolar μ-LED with increasing applied current density. (c) Experimental data and simulation curves for normalized external quantum efficiency of semipolar and c-plane μ-LEDs. (d) Simulated electron current density throughout whole semipolar and c-plane μ-LED structures at 20  A/cm2 and 200  A/cm2 forward current density.

Fig. 4. (a) Fluorescence microscopy image of RGB pixel. (b) Overlap relationship between blue μ-LED electroluminescence emission and absorption of quantum-dot photoresist. (c) Electroluminescence spectra of red and green pixels. (d) Electroluminescence microscope image of RGB pixels.

Fig. 5. Peak wavelengths of c-plane and semipolar μ-LEDs in range 1 to 200  A/cm2 current density.

Fig. 6. Color gamut of RGB pixel assembly from c-plane μ-LED and QDPR under various current densities in (a) CIE 1931 and (b) CIE 1976. Color gamut of RGB pixel assembly from semipolar μ-LED and QDPR under various current densities in (c) CIE 1931 and (d) CIE 1976.