PLASMONIC FIELD-ENHANCED PHOTODETECTOR AND IMAGE SENSOR USING LIGHT ABSORBING LAYER HAVING SPLIT CONDUCTION BAND AND VALENCE BAND
A plasmonic field-enhanced photodetector is disclosed. The photodetector absorbs surface plasmon polaritons (SPPs) by using a light absorbing layer having a conduction band and a valence band in which an energy is split, the SPPs being generated by combining surface plasmons (SPs) with photons of a light wave, and generates photocurrent based on the absorbed SPPs.
1 . A photodetector comprising:
a metal layer configured to shield incident light and generate surface plasmon polaritons (SPPs);
a light absorbing layer configured to use the generated SPPs and allow charges excited by the SPPs and a localized electric field effect to tunnel; and
a dielectric formed at nanoholes in which at least a part of the metal layer is opened;
wherein the SPPs form a localized electric field at an interface where the metal layer meets the dielectric; and
wherein a photocurrent is induced by a localized electric field effect of the absorbed SPPs and tunneling of charges excited by photons of light.
2 . The photodetector according to claim 1 , wherein the light absorbing layer includes a semiconductor having a conduction band and a valence band in which an energy level is split by applying uniaxial tensile stress.
3 . The photodetector according to claim 1 , wherein the metal layer is extended from a surface to the light absorbing layer and guides the generated SPPs to the light absorbing layer.
4 . The photodetector according to claim 2 , wherein in the light absorbing layer, the energy level is split into a heavy hole and a light hole in the valence band.
5 . The photodetector according to claim 2 , wherein the split energy level allows for the sensing of incident light in a wavelength band of 1200 nm or more.
6 . The photodetector according to claim 1 , wherein the SPPs form localized surface plasmons (LSPs) at edges where the metal layer meets the dielectric; and
wherein a density of the localized electric field increases per unit area to increase the photocurrent as a size of the nanoholes decreases.
7 . The photodetector according to claim 1 , wherein the nanoholes are formed of a material containing Si 3 N 4 ; and
wherein the metal layer contains at least one of aluminum (Al), gold (Au), or silver (Ag).
8 . An image sensor comprising:
a metal surface configured to shield incident light and generate surface plasmon polaritons (SPPs);
a metal nanohole array formed on the metal surface; and
a detector array formed at a position corresponding to the metal nanohole array, the detector array comprising the photodetector according to claim 1 .