Stability and interlayer formation at epitaxial p-type oxides/Ga₂O₃ interfaces

Ga₂O₃, a power electronics material, is valued for its wide bandgap (≈ 4.5 eV), high breakdown field (≈ 8 MV/cm), large area substrates, and stability. However, the lack of p-type doping in Ga₂O₃ necessitates heterojunctions with p-type oxides, among which NiO and Cr₂O₃ are promising candidates.^1,2 To date, most studies on Ga₂O₃ based heterojunctions have focused primarily on device optimization rather than on the fundamental understanding of interface dynamics and long-term stability. This work aims to provide a deeper understanding of NiO/Ga₂O₃ and Cr₂O₃/Ga₂O₃ interfaces. A detailed growth campaign for NiO and Cr₂O₃ has been conducted via pulsed laser deposition on Ga₂O₃ substrates with various orientations, i.e., (100), (001), and (−201). X-ray diffraction evaluated material quality and epitaxial relationships, revealing (-201) substrate orientation as common epitaxial match for both oxides. Transmission electron microscopy is used to examine interface stability and possible interlayer formation when thermal treatments are applied, simulating long-term high-temperature operations. Additionally, thermoreflectance measurements are performed to investigate heat dynamics at the interfaces.