Metal-oxide-semiconductor photocapacitor for sensing surface plasmon polaritons

Electronic detection of surface plasmon polaritons by metal-oxide-silicon capacitor

“…The photocurrent peaks close to the SPP resonance angle defined by the minimum in the reflectance curve. The secondary measured peak at higher angles is due to back-reflection from the exit facet of the prism, 6 since the two peaks are symmetric about 45…”

“…5,6 The sign of the transient photocurrent depends on carrier type, the photoresponse is maximum at intermediate resistivity values, and the response can be amplified or extinguished by suitable substrate bias. Combined angle-and wavelength-dependence for resonant excitation of surface plasmons suggests applications to spectral sensing and imaging.…”

“…1 device have previously been published. 5,6 The Ag/air/Au/thermaloxide layers had nominal thicknesses 45/600/30/280 nm. The air-gap provides dielectric contrast necessary to excite SPPs, represented schematically in Fig.…”

“…Namely, the photocurrent is negative for p-type and positive for n-type silicon. 6 For example, electrons that are photo-generated within the depletion region under the metal top contact on p-Si are swept toward the contact by the electric field in the bent-band region.…”

“…The photoresponse is zero for low-resistivity substrates, strongest for intermediate resistivity, and very small for high resisitivity. 6 Minority carriers are photo-excited to a depth ∼1/α, where the absorption coefficient α for Si at 632 nm wavelength has the value 0.31 µm −1 , 15 giving an optical penetration depth of ∼3 µm. Only those minority carriers generated within the depletion region, where there is band bending, contribute to photocurrent.…”