Stabilization of amorphous GaN by oxygen

We have investigated experimentally the structure of disordered GaN films. The results suggest that it is not possible to stabilize an amorphous network in stoichiometric films, and the GaN instead consists of random-stacked nanocrystals of some 3-nm diameter. However, incorporation of 15% or more oxygen stabilizes an amorphous phase, which we attribute to the presence of nontetrahedral bonds centered on oxygen. The ionic favorability of heteropolar bonds and its strikingly simple constraint to even-membered rings are the likely causes of the instability of stoichiometric a-GaN.