Broadly tunable, narrow-linewidth light from a single GaN-based micro-cavity LED (MCLED)

If a single device can emit red, green, and blue (RGB) light, this would imply that within the unit area of a display, not only can the number of devices per unit area and energy consumption be reduced to 1/3, but also the packaging and fabrication costs of the display can be lowered. In this work, we fabricated GaN-based microcavity light-emitting diodes (MC-LEDs). A single device demonstrates the capability to sequentially emit red, green, and blue light as the injection current density varies, with a tunable spectral range of approximately 260 nm, accounting for nearly 70% of the visible light wavelength range. Furthermore, compared with existing devices of similar performance, the emitted spectrum of the device exhibits a narrower linewidth of 3∼8 nm, which is attributed to the wavelength-selective ability of the resonant cavity. The ultra-wide spectrally tunable range originates from a few physical effects such as the screened quantum-confined Stark effect (QCSE) and the carrier band-filling effect in the red quantum well (QW), the Purcell effect in the resonant cavity, and the spontaneous emission from the blue QW. This work may provide a novel solution for the concept of monolithic full-color light sources based on a single device.