Photo-detector

A photodetector, comprising:

• an insulating substrate;
• a material layer on the insulating substrate and extending in a waveguide direction, the material layer having a refractive index higher than that of the insulating substrate;
• a first electrode made of a metal, the first electrode extending in the waveguide direction on a first side of the material layer, and the first electrode being disposed on the insulating substrate and spaced apart from the material layer;
• a core between the material layer and the first electrode, the core having a refractive index lower than that of the material layer, and the core extending in the waveguide direction;
• a second electrode made of a metal and disposed on the insulating substrate on a second side of the material layer, the second electrode being spaced apart from the material layer;
• and
• a light absorption layer electrically connected to the first electrode and the second electrode, the light absorption layer being disposed on the core and made of graphene,
• wherein an interval between the material layer and the second electrode is within a range in which light confinement is possible between the material layer and the first electrode, and
• the interval between the material layer and the second electrode is within a range in which light confinement is not possible between the material layer and the second electrode.

A method, comprising:

• forming a material layer on an insulating substrate, the material layer extending in a waveguide direction, the material layer having a refractive index higher than that of the insulating substrate;
• forming a first electrode on the insulating substrate and spaced apart from the material layer, the first electrode being made of a metal and extending in the waveguide direction on a first side of the material layer, wherein a core is disposed between the material layer and the first electrode, the core having a refractive index lower than that of the material layer, and the core extending in the waveguide direction;
• forming a second electrode on the insulating substrate and spaced apart from the material layer, the second electrode being made of a metal and disposed on a second side of the material layer;
• and
• electrically connecting a light absorption layer to the first electrode and the second electrode, the light absorption layer being disposed on the core and made of graphene,
• wherein an interval between the material layer and the second electrode is within a range in which light confinement is possible between the material layer and the first electrode, and
• the interval between the material layer and the second electrode is within a range in which light confinement is not possible between the material layer and the second electrode.