Equivalent oxide thickness scaling for efficient III-V/Si hybrid MOS optical phase shifter

III-V/Si hybrid metal-oxide-semiconductor (MOS) optical phase shifter, which is enabled by the wafer bonding technology, allows for efficient, low-power and low-loss optical phase control. Reducing the equivalent oxide thickness is effective to enhance its modulation efficiency. In this study, we demonstrated the capacitance equivalent thickness scaling down to 3.5 nm by employing HfO2/Al2O3 stack for wafer bonding, which is expected to results in a $\mathrm{V}_{\pi}\mathrm{L}$ around 0.035 Vcm.