https://phys.org/news/2018-06-nanoscale-patterning-surfaces-possibilities.html

The light-emitting component of LEDs is a surprisingly simple structure, typically a thin layer of a dielectric material such as gallium nitride (GaN) on a crystalline sapphire substrate. This structure means the light emitted by LEDs is inefficiently dispersed in all directions, including back into the substrate on which the light-emitting layer is fixed. So, while researchers have made tremendous advances in light-emitting efficiency, there remains room for improvement.

Egor Khaidarov and colleagues from A*STAR's Data Storage Institute and Nanyang Technological University have now found a way to pattern GaN with nanoscale features that can control the behavior of light.