Unit pixel of image sensor and light-receiving element thereof

An image sensor unit pixel, comprising:

• a light-receiving element which generates an electric current by using change of electric charge quantity caused by incident light;
• and
• a reset element which removes residual electric charges from the light-receiving element,
• wherein the light-receiving element comprises:
• a light-receiving unit which absorbs light;
• an oxide film which contacts a side of the light-receiving unit;
• a source and a drain which stand off the light-receiving unit with the oxide film in between the source and the drain, and the source and the drain facing each other;
• a channel region formed between the source and the drain such that an electric current can be formed between the source and the drain;
• and
• at least one wavelength expanding layer, formed in at least one among the light-receiving unit, the oxide film, and the channel region, and the at least one wavelength expanding layer split energy levels to form a plurality of local energy levels,
• wherein the wavelength expanding layer splits the energy levels of a conduction band and a valence band according to a direction of a crystal lattice arrangement of the wavelength expanding layer.