Graphene-based biosensor

1 . A biosensor comprising:

a substrate;

a source electrode and a drain electrode separated from each other on the substrate;

a graphene layer disposed on the substrate, and including one end connected to the source electrode and the other end connected to the drain electrode;

a first doping layer disposed on one end of the graphene layer;

a second doping layer disposed on the other end of the graphene layer and separated from the first doping layer;

a first passivation layer and a second passivation layer disposed on the first doping layer and the second doping layer, respectively; and

a gate electrode disposed on top of either of the first passivation layer and the second passivation layer and separated from either of the first passivation layer and the second passivation layer,

wherein the first doping layer is applied on the source electrode and one end of the graphene layer, and

wherein the second doping layer is applied on the drain electrode and the other end of the graphene layer.

2 . The biosensor of claim 1 , wherein a portion of the graphene layer is applied by the first doping layer or the second doping layer and by the first passivation layer or the second passivation layer; and

the other portion of the graphene layer is left open without being applied by the first doping layer or the second doping layer and by the first passivation layer or the second passivation layer.

3 . The biosensor of claim 1 , wherein the source electrode is formed on a first area which includes the one end of the graphene layer;

the first doping layer is formed on a second area adjacent to the first area of the graphene layer;

the first doping layer and the first passivation layer are not applied on a third area adjacent to the second area of the graphene layer;

the second doping layer is formed on a fourth area adjacent to the third area of the graphene layer; and

the drain electrode is formed on a fifth area which includes the other end of the graphene layer and is adjacent to the fourth area.

4 . The biosensor of claim 3 , wherein a length of the second area or the fourth area of the graphene layer is shorter than a length of the third area.

5 . The biosensor of claim 3 , wherein a length of the second area or the fourth area of the graphene layer is less than or equal to 100 nm.

6 . The biosensor of claim 3 , wherein a length of the second area or the fourth area of the graphene layer is longer than a length of the first area or the fifth area of the graphene layer.

7 . The biosensor of claim 3 , wherein, as a resistance of the second area or the fourth area of the graphene layer decreases, a conductivity of the graphene layer increases.

8 . The biosensor of claim 3 , wherein, as a length of the third area of the graphene layer increases, a conductivity of the graphene layer increases.

9 . The biosensor of claim 3 , wherein, as a ratio of a length of the second area or the fourth area of the graphene layer to a length of the third area of the graphene layer decreases, a conductivity of the graphene layer increases.

10 . The biosensor of claim 3 , wherein a height of the graphene layer is less than a height of the substrate.

11 . The biosensor of claim 3 , wherein, as a length of the third area of the graphene layer decreases, a height of the graphene layer decreases or a height of the first doping layer or a height of the second doping layer increases.

12 . The biosensor of claim 1 , wherein the first doping layer or the second doping layer includes an organic compound or an inorganic compound, and the inorganic compound includes at least one of WO3, MoO3, or ZnO.

13 . The biosensor of claim 1 , further comprising an insulating layer disposed on the substrate, wherein the source electrode, the drain electrode, and the graphene layer are disposed on the insulating layer.

14 . A biosensor comprising:

a substrate;

a source electrode and a drain electrode separated from each other on the substrate;

a graphene layer disposed on the substrate, and including one end connected to the source electrode and the other end connected to the drain electrode;

a first doping layer and a second doping layer applied on a portion of the graphene layer and separated from each other thereon;

a first passivation layer and a second passivation layer disposed on the first doping layer and the second doping layer, respectively; and

a gate electrode disposed on top of either of the first passivation layer and the second passivation layer and separated from either of the first passivation layer and the second passivation layer,

wherein the first doping layer is applied on the source electrode and one end of the graphene layer, and

wherein the second doping layer is applied on the drain electrode and the other end of the graphene layer.

15 . The biosensor of claim 1 , wherein the first doping layer is applied directly on a top surface of the source electrode and directly on a top surface of one end of the graphene layer, and

the second doping layer is applied directly on a top surface of the drain electrode and directly on a top surface of the other end of the graphene layer.

16 . The biosensor of claim 1 , wherein the first doping layer directly contacts both the source electrode and graphene layer, and

the second doping layer directly contacts the drain electrode and the graphene layer.

17 . The biosensor of claim 1 , wherein the first doping layer is disposed directly between the source electrode and the first passivation layer, and

the second doping layer is disposed directly between the drain electrode and the second passivation layer.

18 . The biosensor of claim 1 , wherein the first doping layer comprises a step shape to directly contact the one end of the graphene layer,

wherein the second doping layer comprises a step shape and directly contacts the other end of the graphene layer,

wherein the one end of the graphene layer extends passed the step shape of the first doping layer, and

wherein the other end of the graphene layer extends passed the step shape of the second doping layer.