Heteroepitaxial $\Epsilon-\Text{ga}_{2}\mathrm{o}_{3}$ MOSFETs on a 4-Inch Sapphire Substrate with a Power Figure of Merit of 0.29 $\Text{gw}/\text{cm}^{2}$

We have designed and fabricated a high-voltage metal-oxide-semiconductor field effect transistor (MOSFET) based on heteroepitaxial $\varepsilon-\text{Ga}_{2}\mathrm{O}_{3}$ . The high-quality unintentionally-doped (UID) $\varepsilon-\text{Ga}_{2}\mathrm{O}_{3}$ film was grown by metalorganic chemical vapor deposition (MOCVD) on a 4-inch sapphire substrate. Through an optimized fluorine-plasma treatment process, we achieved high-density surface doping with a carrier sheet density $(n_{s})$ exceeding $10^{14}\text{cm}^{-2}$ and mobility of 32 $\text{cm}^{2}/\mathrm{V}\cdot \mathrm{s}$ . We proposed a dual-density channel design for the $\varepsilon, \text{Ga}_2\mathrm{O}_{3}$ MOSFETs, which involved high-density doping in the access region to reduce the parasitic resistance and low-density doping under the gate to ensure device pitch-off. This concept was verified using TCAD simulation before device fabrication. The fabricated $\varepsilon-\text{Ga}_{2}\mathrm{O}_{3}$ MOSFETs, with a gate-to-drain spacing $(L_{GD})$ of $10 [\iota \mathrm{m}$ , exhibited a high breakdown voltage $(V_{br})$ of $2.85 \text{kV}$ and a specific on-resistance $(R_{on,sp})$ of 27.6 $\mathrm{m}\Omega\cdot \text{cm}^{2}$ , yielding a power figure of merit (PFOM) of 0.29 $\text{GW}/\text{cm}^{2}$ . This PFOM value is the highest reported value for heteroepitaxial $\text{Ga}_2\mathrm{O}_{3}$ devices and among the best in homoepitaxial $\beta-\text{Ga}_{2}\mathrm{O}_{3}$ lateral FETs.