Fabrication of gallium nitride-based light devices with physical vapor deposition (PVD)-formed aluminum nitride buffer layers is described. Process conditions for a PVD AlN buffer layer are also described. Substrate pretreatments for a PVD aluminum nitride buffer layer are also described. In an example, a method of fabricating a buffer layer above a substrate involves pre-treating a surface of a substrate. The method also involves, subsequently, reactive sputtering an aluminum nitride (AlN) layer on the surface of the substrate from an aluminum-containing target housed in a physical vapor deposition (PVD) chamber with a nitrogen-based gas or plasma.