Evaluation of AlN insertion layer on the properties of heterogeneous integrated Ga2O3 films on sapphire

Integration of gallium oxide (Ga₂O₃) with highly thermal conductive AlN/sapphire substrate is more effective to dissipate heat in the Ga₂O₃-based devices. In this work, the properties of Ga₂O₃ films grown on sapphire and AlN/sapphire substrates via MOCVD were both examined via various experimental methods. The X-ray diffraction (XRD) analysis showed good crystallinity and different orientations of Ga₂O₃ and AlN thin films. The absorption properties and band gaps were extracted from UV/Vis spectra. The atomic force microscopy (AFM) scanning images showed smooth Ga₂O₃ surfaces on sapphire and AlN/sapphire substrates (RMSs of 2.4 nm and 4.8 nm, respectively). The scanning electron microscopy (SEM) highlighted well-defined grains of Ga₂O₃ and distinct boundaries of both heterostructures. X-ray photoelectron spectroscopy (XPS) analysis depicted the distributions of various components throughout the films. Finally, by using the time-domain thermoreflectance (TDTR) method, the thermal conductivity and the thermal boundary conductivity of Ga₂O₃ without AlN interlayer were found to be 3.1 W/(m·K) and 70.1 MW/(m²·K) respectively. By comparison, adding AlN interlayer made the thermal conductivity and thermal boundary conductivity rise to 3.3 W/(m·K) and 111.5 MW/(m²·K) respectively. These findings have demonstrated the high-quality Ga₂O₃/AlN integration and good heat dissipation provided by AlN interlayer, opening up new prospects for Ga₂O₃/AlN devices in the future.