Efficient optical phase modulator based on an III-V metal-oxide-semiconductor structure with a doped graphene transparent electrode

We propose a III-V metal-oxide-semiconductor (MOS) optical modulator with a graphene gate electrode along with the analysis of the modulation properties. With p-type doped graphene used as a transparent gate electrode, we can fully utilize the electron-induced refractive index change in an n-type InGaAsP waveguide with the reduction of the hole-induced optical absorption observed in a III-V/Si hybrid MOS optical modulator. Numerical analysis displays that up to the phase modulation efficiency of 0.82 V center dot cm and 0.22 dB optical loss for pi phase shift can be achieved when the gate oxide thickness is 100 nm. With the elimination of the unnecessary parasitic capacitance found in the overlapping of graphene on the slab part of the waveguide, in conjunction with the high electron mobility in InGaAsP, the device also enables a modulation bandwidth of greater than 200 GHz.