A novel red LED using Eu-doped GaN is a promising component for next-generation display with ultrasmall-size, full-color, and high-resolution. The LED exhibits narrow-band red emission and the wavelength is almost independent of ambient temperature and injected current. The size dependence of emission efficiency is negligibly small compared with conventional AlInGaP-based red LEDs. We also demonstrated monolithic integration of vertically stacked full-color LEDs.