Ferroelectric modulation of terahertz waves with graphene/ultrathin-Si:HfO2/Si structures.

Ferroelectric-field-effect-tunable modulation of terahertz waves in graphene/Si:HfO₂/Si stack structure was observed. The modulation shows distinct behaviors when the samples under different gate polarities. At a negative voltage, a transmission modulation depth up to ~74% was present without depending on the photo illumination power, whereas, at a positive voltage, the modulation of Thz wave shows dependence on the illumination power, which is ascribed to the creation/ elimination of an extra barrier in Si layer in response to the polarization in the ferroelectric Si:HfO₂ layer. Considering the good compatibility of HfO₂ on Si-based semiconductor process, the ferroelectricity layer of Si:HfO₂ may open up an avenue for the tunable modulation of Thz wave. [ABSTRACT FROM AUTHOR]