Unit pixel of image sensor and photo detector thereof

A photo detector configured to absorb light in a unit pixel of an image sensor transforming the absorbed light to an electrical signal, comprising:

• a light-absorbing part configured to absorb light by being formed in a floated structure;
• an oxide film being in contact with one surface of the light-absorbing part;
• a source being in contact with one side of the other surface of the oxide film and separated from the light-absorbing part with the oxide film therebetween;
• a drain facing the source so as to be in contact with the other side of the other surface of the oxide film and separated from the light-absorbing part with the oxide film therebetween;
• and
• a channel interposed between the source and the drain and configured to form flow of an electric current between the source and the drain,
• wherein the light-absorbing part is doped with first type impurities, and the source and the drain are doped with second type impurities,
• wherein the light-absorbing part is insulated from the source and the drain by the oxide film,
• wherein electrons of electron-hole pairs generated by the absorbed light are moved to the source and the drain by a tunneling phenomenon occurred by an electric field concentrated in the oxide film, and the flow of the electric current of the channel is controlled by a change in the quantity of electric charge of the light-absorbing part caused by the moving of the electrons.