Energy Efficient Micro-LED Displays: A Survey

(Summary) Micro LED display that provides high light emission efficiency through better utilization of the LED emitter structures. The display has a substrate with electrode structures connected to circuitry within the substrate. An LED functional layer above the substrate contains isolated LED structures that correspond to the electrode structures. The LED structures can emit light individually. An electrode layer covers the LED layer and micro lenses focus light from each LED structure. This allows each isolated LED structure to be fully used as a pixel emitter, improving light extraction compared to shared LED regions. The isolated LED structures are electrically connected to the substrate electrodes. The display is manufactured by etching openings through the LED layer and substrate, filling them with metal pillars, and depositing the electrode and lens layers.

(Summary) Fabricating integrated multi-color LED display panels using techniques that enable high-resolution displays with low power consumption. The method involves stacking multiple layers of microLEDs on top of each other with each layer bonded and patterned to form microLED arrays. This allows integration of pixel driver circuitry with the microLEDs. The stacking enables dense pixel packing with one microLED layer per color.

(Summary) An LED structure for better light extraction in displays by using hexagon shaped LEDs mounted within circular reflective wells. The hexagon shape allows a closer fit to the circular wells compared to square LEDs, increasing light extraction efficiency. The compact fit enables more compact pixel staggering and resolution in displays.

(Summary) MicroLED devices that have their crystal lattice structure arranged such that the c-plane of the crystal lattice is misaligned with respect to the light emitting surface. This off-axis crystal structure guides the light generated inside the LED to exit the emission surface at an angle less than the critical angle for total internal reflection. This improves the extraction efficiency of the LED and increases the light output.

(Summary) Method for improving light extraction efficiency of remote phosphor LED lamps by laser processing the phosphor crystal. The phosphor crystal is ablated with laser to create microstructure arrays on the surface. This roughens the surface to scatter light out more effectively. The laser ablation creates ordered patterns of microstructures on the phosphor crystal surface. This increases light extraction efficiency by allowing more light to escape the crystal instead of being internally reflected back. The patterns can be tailored to optimize light extraction.

(Summary) Micro LED display with improved efficiency and color accuracy over conventional designs. The micro LED is formed by growing a buffer layer column on a substrate, then sequentially forming the layers of the LED on the buffer layer column. After that, electrodes are added on the inner and outer sides of the LED structure. This creates a micro LED that is shaped like a tube with hollow center. The tube structure lowers impedance between the electrodes, improving conductivity and efficiency. The tube shape also increases effective junction area and current density, improving color accuracy.

(Summary) A technique to produce high efficiency micro-LED displays with lower manufacturing costs. The technique involves monolithically growing different colored micro-LEDs on the same wafer and transferring them to the display backplane to form pixels. This eliminates the need for separate growth and transfer steps for each micro-LED color. For example, blue and green micro-LEDs can be grown together in a "BG" structure, then transferred as a unit to the backplane.

(Summary) Improving the efficiency and lifetime of microLED displays by passivating the LED structures. A passivation layer over the sidewall of the multiple quantum well (MQW) LED structure helps maintain LED quality after etching, without degrading performance. The passivation material includes III-Nitride compounds like AlN for compatibility with GaN-based microLEDs. It can be deposited at low temperature after MQW patterning. The passivation layer protects the sidewalls from damage during subsequent processing, improving LED performance and lifetime compared to unpassivated structures.

(Summary) A low power consumption high brightness display with an integrated LED micro-display that provides efficient light generation and color conversion. The display features an array of red, green, and blue LEDs with color conversion layers to create a full color display. The LEDs are directly integrated on a substrate with electronic driving circuitry. This eliminates the need for external light sources and components, reducing power consumption compared to displays using separate LEDs and pattern generators. The integrated design also allows precise matching of LED emission wavelengths for optimal color quality.