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Wafer bonding ofβ‐Ga₂O₃and N‐polar GaN single crystal substrates is demonstrated by adding ZnO as a “glue” interlayer. The wafers are fully bonded such that Newton rings are not observed. Temperature‐dependent current‐voltage (I–V) measurements are conducted on the as‐bonded Ga₂O₃/ZnO/N‐polar GaN test structure and after annealing at 600 °C and 1100 °C. The impact of post‐annealing temperature on the electrical and structural characteristics of the bonded samples is investigated. A consistently ohmic‐like characteristic is obtained by annealing the bonded wafers at 1100 °C in N_2,which is in part due to crystallization of ZnO and diffusion of Ga into ZnO which makes it n‐type doped. The wafer bonding ofβ‐Ga₂O₃and GaN achieved in this work is promising to combine the material merits of both GaN and Ga₂O₃targeting breakthrough high‐frequency and high‐power device performances.

Direct wafer bonding of β-Ga₂O₃and N-polar GaN at a low temperature was achieved by acid treatment and atmospheric plasma activation. The β-Ga₂O₃/GaN surfaces were atomically bonded without any loss in crystalline quality at the interface. The impact of post-annealing temperature on the quality of bonding interfaces was investigated. Post-annealing at temperatures higher than 700 °C increases the area of voids at bonded interfaces probably due to the difference in the coefficient of thermal expansion. The integration of β-Ga₂O₃on the GaN substrate achieved in this work is one of the promising approaches to combine the material merits of both GaN and Ga₂O₃targeting the fabrication of novel GaN/β-Ga₂O₃high-frequency and high-power electronics as well as optoelectronic devices.