Investigation of gallium oxide thin film hetero-integrated with bulk diamond via atomic layer deposition

In this work, the characteristics of the gallium oxide (Ga2O3)/diamond heterostructure were thoroughly examined after the preparation of Ga2O3 thin film on bulk diamond via atomic layer deposition. The X-ray diffraction (XRD) analysis revealed the Ga2O3 film amorphous and diamond polycrystalline. The atomic force microscopy (AFM) mapping displayed remarkably smooth surfaces of the Ga2O3 film and diamond substrate (RMS of 0.184 and 0.508 nm, respectively). The scanning electron microscopy (SEM) images showed conspicuous grains formed on the diamond, and small crystallites on the surface of the film. The optical characteristics were investigated via spectroscopic ellipsometry (SE) and UV/Vis/NIR spectrophotometer. Raman spectroscopy suggested a sharp diamond-related (sp3) peak and an extremely weak bulge band around 1350–1620 cm−1. X-ray photoelectron spectroscopy (XPS) analysis indicated Ga2O3/diamond heterojunction to be staggered (type II) band alignment with valence band and conduction band offsets of around 1.18 eV and 2.09 eV, respectively. Moreover, according to time-domain thermoreflectance (TDTR) measurements, the thermal conductivity of Ga2O3 and the thermal boundary conductivity of the heterointerface were 5.13 W/(m·K) and 19.22 MW/(m2·K), respectively. These findings not only demonstrate the feasibility of Ga2O3-on-diamond hetero-integration but open up new prospects for the design and physical analysis of Ga2O3/diamond-based devices in the future.