High-efficiency UV LEDs on sapphire

We discuss factors affecting the external quantum efficiency, droop and reliability of AlGaN deep ultraviolet (DUV) light emitting diodes (LED) grown on sapphire substrates. Improvement of LED performance is achieved by suppression of the nonradiative recombination in epitaxial structures with dislocation density reduced to below 5x108 cm-2, transparent LED structure design and optimized UV encapsulation for enhanced light extraction. Relatively low light extraction efficiency remains to be a key factor limiting LED output power and quantum efficiency.

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