Self-forming and self-decomposing gallium oxide layers at the GaN/Al2O3 interfaces

We examine the energy band diagram at the interface between GaN and Al 2 O 3 containing negatively-charged oxygen interstitial ( O i 2 − ) defects. At a p-type GaN (p-GaN)/Al 2 O 3 interface, oxygen atoms and electrons are emitted from the O i 2 − defects causing interfacial oxidation resulting in the self-formation of a p-GaN/Ga 2 O 3 /Al 2 O 3 structure. On the other hand, such the reactions do not occur at an n-type GaN (n-GaN)/Al 2 O 3 interface. Moreover, when n-GaN/Ga 2 O 3 /Al 2 O 3 structures are formed, the Ga 2 O 3 layers spontaneously decompose to form O i 2 − defects in the Al 2 O 3 . Consequently, our proposed Ga 2 O 3 formation mechanism gives completely different results for p-GaN/Al 2 O 3 and n-GaN/Al 2 O 3 interfaces.