Oxygen controlled PVD AlN buffers for GaN-based optoelectronic and electronic devices is described. Methods of forming a PVD AlN buffer for GaN-based optoelectronic and electronic devices in an oxygen controlled manner are also described. In an example, a method of forming an aluminum nitride (AlN) buffer layer for GaN-based optoelectronic or electronic devices involves reactive sputtering an AlN layer above a substrate, the reactive sputtering involving reacting an aluminum-containing target housed in a physical vapor deposition (PVD) chamber with a nitrogen-containing gas or a plasma based on a nitrogen-containing gas. The method further involves incorporating oxygen into the AlN layer.