First Demonstration of ε-Ga₂O₃/α-Ga₂O₃ HFET With a Sn-Doped Channel

This study presents the $\varepsilon $ -Ga2O3/ $\alpha $ -Ga2O3 heterostructure field-effect transistor (HFET) with a Sn-doped channel on a c-plane sapphire substrate using mist-CVD for the first time. $\varepsilon $ -Ga2O3forms on the Sn-doped layer only when a c-plane sapphire substrate is used, a phenomenon absent from r-plane sapphire substrates. Secondary ion mass spectroscopy (SIMS) reveals that the Sn-doped layer in $\varepsilon $ -Ga2O3/ $\alpha $ -Ga2O3 exhibits a smaller Sn diffusion range compared to $\alpha $ -Ga2O3 homojunction, yet achieves lower sheet resistance, which may be attributed to a potential polarization effect in $\varepsilon $ -Ga2O3/ $\alpha $ -Ga2O3 heterojunction. The $\varepsilon $ -Ga2O3/ $\alpha $ -Ga2O3 HFET demonstrates superior performance, including a breakdown voltage of 1725 V, a specific on-resistance of 49.2 m $\Omega \cdot $ cm2, and a power figure-of-merit of 60.48 MW/cm2, indicating its strong potential for power electronics applications.