Structure of the very first atomic layer of Ga oxide on GaN at GaN oxidation front

The atomic structure of the GaN oxidation front formed by oxide deposition followed by annealing was analyzed using atomic-resolution transmission electron microscopy and first-principles calculations. The oxidation front displays a terrace-step morphology, with atomically flat terraces and GaN monolayer steps. Our analysis clearly demonstrates that oxidation produces an epitaxial Ga oxide layer atop GaN. Furthermore, interfacial Ga atoms are situated near stacking fault positions of the underlying GaN lattice, forming dislocation-like structures at interface steps. These structural imperfections are expected to introduce states within the bandgap, offering insights into strategies for improving the electronic properties of GaN-based metal–oxide–semiconductor interfaces.