Enhanced performance of normally-off AlGaN/GaN MOS-HEMTs taking advantage of extreme-k BaTiO3 with prominent dielectric polarization

In the letter, we demonstrate that the performance enhancement of normally-off AlGaN/GaN metal–oxide–semiconductor-high-electron-mobility transistors (MOS-HEMTs) benefits from the prominent dielectric polarization of extreme-k BaTiO3. The fabricated HEMTs exhibit a high threshold voltage of 1.67 V, attributed to the additional negative polarization bound charges at the BaTiO3/AlGaN interface and the resulting expansion of depletion width under negative gate bias. A relatively large saturation output current of 374 mA/mm is also achieved thanks to the additional positive polarization bound charges and the resulting enhancement of channel electron concentration under positive gate bias. Further, the extremely high dielectric constant of BaTiO3 and the corresponding capacitive coupling effect enable a notable improvement in channel controllability, achieving a high maximum transconductance of 108.7 mS/mm and a small subthreshold swing of 69.6 mV/dec. The proposed BaTiO3-MOS-HEMTs with fine post-etch treatments also exhibit low gate leakage, a competitive breakdown field of 1.4 MV/cm, and a high Baliga's figure-of-merit of 1.05 GW/cm2. These findings elucidate the substantial potential of extreme-k BaTiO3 for high-performance normally-off AlGaN/GaN power switching applications.