Heteroepitaxial Growth of Single-Crystalline β-Ga2O3 on GaN/Al2O3 Using MOCVD

In-planeatomic arrangements of nitrogen (N) atoms of GaN(bottom) and oxygen (O) atoms of Ga2O3 (top),showing that & beta;-Ga2O3 forms a six-foldin-plane rotational domain. The formation of n-Ga2O3/p-GaN heterojunctions has been studied intensivelydue to the lack of p-Ga2O3.Metalorganic chemical vapor deposition (MOCVD) is known to providea high-quality heterojunction of n-Ga2O3/p-GaN compared to thermal oxidation,sputtering, or pulsed-laser deposition (PLD). In this work, single-crystalline & beta;-Ga2O3 of {-201} is grown on aGaN (001)/Al2O3 substrate using MOCVD. An abruptheterojunction without a noticeable interfacial layer is observedbetween & beta;-Ga2O3 and GaN. However, dueto the lattice mismatch between & beta;-Ga2O3 (-201) and GaN (001), grain boundaries and grain defectsoriginating from the Ga2O3/GaN interface continuein & beta;-Ga2O3 in a diagonal direction. Theepitaxial nature of the grown & beta;-Ga2O3 onthe GaN (001)/Al2O3 substrate causes the nanorod-shapedmorphology in the growth direction of & beta;-Ga2O3. This work marks a step toward the formation of a high-qualityheterojunction of Ga2O3/GaN, which would serveas an essential building block for various devices, including optoelectronicsand power electronics.