Thermal properties of Ga2O3 thin films and devices prepared on sapphire and SiC substrates by liquid-injection MOCVD

Gallium oxide (Ga₂O₃) is a promising ultra-wide bandgap (UWBG) semiconductor that was quickly recognised as a suitable material for fabrication of optoelectronic devices or high-power rectifiers and switches, potentially greatly exceeding the capabilities of mainstream Si, GaN, and SiC. Despite many advantageous material properties, large-area bulk Ga₂O₃ substrates remain expensive, and Ga₂O₃ itself suffers from low lattice thermal conductivity – crucial for an efficient heat extraction from the active device area, generated by Joule losses during the on-state operating conditions. Heteroepitaxy of Ga₂O₃ films offers a possible route for a low-cost production of Ga₂O₃-based power or optoelectronic devices if e.g. sapphire substrates are used, or much improved thermal performance if highly-thermally-conductive substrates such as SiC or polycrystalline diamond are used. In this work we use liquid-injection metalorganic chemical vapour deposition (LI-MOCVD) to grow thin Ga₂O₃ films on sapphire and 4H-SiC and to fabricate depletion-mode metal-oxide-semiconductor field-effect transistors (MOSFETs). Structural and transport properties of the Ga₂O₃ films and devices prepared on both substrates are analysed. Then, thermal properties of grown Ga₂O₃ films, and Ga₂O₃/SiC and Ga₂O₃/sapphire interfaces are presented and implications for Ga₂O₃-based devices are outlined.