Heteroepitaxial growth of Ga₂O₃ on 4H-SiC by liquid-injection MOCVD for improved thermal management of Ga₂O₃ power devices

We report on the growth of monoclinic β- and orthorhombic κ-phase Ga₂O₃ thin films using liquid-injection metal-organic chemical vapor deposition on highly thermally conductive 4H-SiC substrates using gallium (III) acetylacetonate or tris(2,2,6,6-tetramethyl-3,5-heptanedionato) gallium (III). Both gallium precursors produced the β phase, while only the use of the latter led to growth of κ-Ga2O3. Regardless of the used precursor, best results for β-Ga₂O₃ were achieved at a growth temperature of 700 °C and O₂ flows in the range of 600–800 SCCM. A relatively narrow growth window was found for κ-Ga₂O₃, and best results were achieved for growth temperatures of 600 °C and the O2 flow of 800 SCCM. While phase-pure β-Ga₂O₃ was prepared, κ-Ga₂O₃ showed various degrees of parasitic β phase inclusions. X-ray diffraction and transmission electron microscopy confirmed a highly textured structure of β- and κ-Ga₂O₃ layers resulting from the presence of multiple in-plane domain orientations. Thermal conductivities of 53 nm-thick β-Ga₂O₃ (2.13 + 0.29/−0.51 W/m K) and 45 nm-thick κ-Ga₂O₃ (1.23 + 0.22/−0.26 W/m K) were determined by transient thermoreflectance and implications for device applications were assessed. Presented results suggest great potential of heterointegration of Ga₂O₃ and SiC for improved thermal management and reliability of future Ga₂O₃-based high power devices.