Enhancement of AlGaN/GaN Grating-Gate Terahertz Plasmonic Crystal Functionality Using Graphene

We experimentally studied the optical properties of a new type of AlGaN/GaN grating-gate terahertz plasmonic crystals with and without graphene on the top of the metal grating. It was found that CVD graphene removes the localized plasmon mode observed in the plasmonic crystals without graphene at the gate voltages below the threshold and only weakly affects the delocalized modes seen above the threshold. These effects were explained by the high resistance of the CVD graphene, which does not screen the plasmon modes but provides good control of the electron concentration at the AlGaN/GaN interface due to the Schottky barrier formed on AlGaN.