Gallium nitride is a simple compound which doesn't exist in nature. It is a very strongly chemical bonding material with the most remarkable properties.
Upon adding indium to it and passing a tiny electronic current through gallium nitride, you can get out any color light you want. If you add some aluminium, you get into the ultraviolet.
This is really fascinating because the right ultraviolet wavelength kills all bacteria and viruses. It actually damages the nucleic acid, which is part of DNA and RNA. It can be used for water purification in the developing world. UV sterilization could also be useful in the developed world to replace chlorination.
Furthermore, gallium nitride could be used as an energy saver in power electronic devides that surround us as it is highly efficient compared to silican power electronis devices.
In short: Gallium nitride is a wonderful material with many applications that have remained unknown or unused for now.