Optical properties of GaN: from free excitons in the bulk to confined negatively charged excitons in quantum dots grown by molecular beam epitaxy

After reviewing fourtty years investigations of the optical properties of GaN bulk and thin film crystals grown along any crystallographic directions, I finally address the low dimensional systems and in particular, the optical properties of GaN quantum dots grown by molecular beam epitaxy and that are surprisingly compatible with recombinations of negatively charged excitons.