Red-green-blue (RGB) full-color micro light-emitting diodes (μ-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The semipolar (20-21) InGaN/GaN μ-LEDs were fabricated on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. The semipolar μ-LEDs showed a 3.2 nm peak wavelength shift and a 14.7% efficiency droop under 200A/cm2 injected current density, indicating significant amelioration of the quantum-confined Stark effect. Because of the semipolar μ-LEDs’ emission-wavelength stability, the RGB pixel showed little color shift with current density and achieved a wide color gamut (114.4% NTSC space and 85.4% Rec. 2020).

Full-color displays based on micro light-emitting diodes (μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring (NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al2O3 layer was deposited on the sidewall of NR-μLEDs, which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.

In this study, a full-color emission red–green–blue (RGB) quantum-dot (QD)-based micro-light-emitting-diode (micro-LED) array with the reduced optical cross-talk effect by a photoresist mold has been demonstrated. The UV micro-LED array is used as an efficient excitation source for the QDs. The aerosol jet technique provides a narrow linewidth on the micrometer scale for a precise jet of QDs on the micro-LEDs. To reduce the optical cross-talk effect, a simple lithography method and photoresist are used to fabricate the mold, which consists of a window for QD jetting and a blocking wall for cross-talk reduction. The cross-talk effect of the well-confined QDs in the window is confirmed by a fluorescence microscope, which shows clear separation between QD pixels. A distributed Bragg reflector is covered on the micro-LED array and the QDs’ jetted mold to further increase the reuse of UV light. The enhanced light emission of the QDs is 5%, 32%, and 23% for blue, green, and red QDs, respectively.