Unique Bias Stress Instability of Heterogeneous Ga2O3-on-SiC MOSFET

In this letter, we report on a unique positive bias stress (PBS) instability observed in the heterogeneous Ga2O3-on-SiC (GaOSiC) metal-oxide-semiconductor field-effect transistor (MOSFET). The Ga2O3 layer in the GaOSiC MOSFET, which was fabricated using the ion implantation process, still contains hydrogen (H), leading to significantly different threshold voltage ( ${V}_{\text {TH}}{)}$ shifts and on-resistance ( ${R}_{\text {ON}}{)}$ variations compared to transistors on Ga2O3 bulk under PBS. During the initial several tens of seconds of PBS, the GaOSiC MOSFET exhibits a normal positive ${V}_{\text {TH}}$ shift, resulting from the capture of some electrons in the channel by border traps in the gate dielectric and interface traps. However, as the PBS time increases, the ${V}_{\text {TH}}$ of the GaOSiC transistor starts to shift in the negative direction. This can be attributed to the generation of shallow donors under PBS, with the presence of H, resulting in an increased carrier density ( ${n}_{\text {e}}{)}$ in the Ga2O3 channel. The increased ${n}_{\text {e}}$ also leads to an improvement in drain current and a reduction in ${R}_{\text {ON}}$ of the GaOSiC MOSFET during long-term PBS. Our work provides new insights into the PBS instability of heterogeneous GaOSiC MOSFETs, particularly for high-power applications.