Improved lateral figure-of-merit of heteroepitaxial α-Ga2O3 power MOSFET using ferroelectric AlScN gate stack

In this Letter, we demonstrate heteroepitaxial alpha-Ga2O3 MOSFETs using an aluminum scandium nitride (AlScN) ferroelectric gate stack. Owing to ferroelectric effects, alpha-Ga2O3 MOSFETs with the AlScN/HfO2 gate stack (FGFET) exhibited enhanced electrical performance compared with a HfO2 gate dielectric (IGFET) for variable gate-drain lengths (10, 15, 20 mu m). A remnant polarization value of the AlScN deposited on a HfO2 layer was measured to be about 30 mu C/cm(2). The subthreshold swing (SS) and field-effect mobility (mu(FE)) of IGFET was extracted at 1814 mV/dec and 13.9 cm(2)/V s, respectively. However, the FGFET exhibits a reduced SS of 552 mV/dec with enhanced mu(FE) of 42.7 cm(2)/V s owing to the negative capacitance of the ferroelectric AlScN. Furthermore, a lateral figure-of-merit of 17.8 MW/cm(2) was achieved for the FGFET, far surpassing the 8.3 MW/cm(2) of the IGFET. The proposed ferroelectric AlScN/HfO2 stack can be a promising gate structure for improving both transfer and breakdown characteristics in heteroepitaxial alpha-Ga2O3 power devices.