GaN-based light-emitting diodes (LEDs) have attracted considerable interest for their applications in solid state lighting, automotive front lighting, and full-colour displays because of their high luminous efficiency, low energy consumption, long operation lifetime, and broad spectral range spanning from ultraviolet to red wavelengths. The large lattice and thermal mismatch between Al(Ga)N epilayers and the substrate results in high threading dislocation density in the epilayers. Dislocations propagating into multiple quantum wells (MQWs) act as non-radiative recombination centers that significantly deteriorate the internal quantum efficiency. In addition, owing to the large different in refractive indices between GaN and surrounding air, the light extraction efficiency of GaN-based LEDs is low caused by the total internal reflection (TIR) of the emanated light at the GaN/air interface. The poor internal quantum efficiency and low light extraction efficiency constitute the bottlenecks in realizing high performance devices. This talk will outline the emerging challenges in the design and fabrication of micro/nano-structures for improving light extraction efficiency of GaN-based blue/green/ultraviolet LEDs. Recent advances from our group in developing light-outcoupling micro/nano-structures, such as nanometer-scale V-pits, 3D patterned dual-layer ITO, nanoscale patterned sapphire substrate, patterned sapphire with silica array, wavy sidewall, sidewall nano-prisms, embedded air voids, microstructured SiO~2~ array, and metal wire gird transparent conductive electrode will be discussed. Moreover, the recent development in fabricating flip-chip LED, vertical LEDs, and Mini/Micro-LEDs will also be introduced.


Recent Advances in High-Efficiency Nitride-Based Blue/green/ultraviolet Light-Emitting Diodes

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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