Demonstration of High-Current E-Mode MOSFETs Using Heteroepitaxial ε-Ga₂O₃ on 4H-SiC Substrates

High-current enhancement mode (E-mode) metal-oxide-semiconductor field effect transistors (MOSFETs) have been demonstrated using heteroepitaxial $\varepsilon $ -Ga2O3 on 4H-SiC substrates. The devices featured an unintentionally-doped (UID) channel and ultra-highly conductive access regions, which were realized by a selective-area fluorine-plasma surface doping process. In the access regions, a high sheet carrier concentration ( ${n}_{\text {s}}\text {)}$ exceeding ${3}\times {10} ^{{14}}$ cm−2 combined with a mobility of 47.1 cm2/V $\cdot $ s was achieved, significantly reducing the parasitic resistance. The fabricated E-mode MOSFET with a channel length ( ${L}_{\text {CH}}\text {)}$ of $2~\mu $ m exhibited a high maximum drain current density ( ${I}_{\text {DS, max}}\text {)}$ of 209 mA/mm, a positive threshold voltage ( ${V}_{\text {th}}\text {)}$ of 2.7 V, a large peak transconductance ( ${G}_{\text {m, max}}\text {)}$ of 42 mS/mm, and a high on/off current ratio ( ${I}_{\text {on}}$ / ${I}_{\text {off}}\text {)}$ exceeding $10^{{7}}$ . These competitive performance metrics are mainly attributed to the low parasitic resistance in the access regions and the high thermal conductivity of the 4H-SiC substrate, highlighting the great potential of heteroepitaxial $\varepsilon $ -Ga2O3-on-4H-SiC MOSFETs for high-power and high-frequency applications.