Atomic-scale observation of native oxides on <i>c</i> - and <i>m</i> -faced GaN surfaces

Controlling the dielectric/semiconductor interfaces is essential for the development of semiconductor power devices. Gallium nitride (GaN) has attracted significant attention as a next-generation semiconductor owing to its superior properties; however, controlling the dielectric/GaN interface remains a critical challenge, unlike silicon (Si). In this study, we observed native oxides formed on both the c-face and m-face GaN surfaces after simple air exposure using scanning transmission electron microscopy. Oxygen diffusion into the Si crystal was significantly suppressed by the formation of a SiOx layer; on the other hand, gradual oxygen diffusion (Ga–N–O layer) with a depth of ∼2.0 nm into the GaN crystal was observed. Remarkably, a 1.5 times larger amount of oxygen was incorporated in the m-face GaN than in the c-face GaN. These findings provide key insights into the control of dielectric/GaN interfaces and may facilitate the development of GaN-based power devices.