Abstract
Silicon is an indispensable material in electric device technology. However, Si is an indirect bandgap material; therefore, its excitation efficiency, which requires phonon assistance, is low under propagating far-field light. To improve the excitation efficiency, herein we performed optical near-field excitation, which is confined in a nano-scale, where the interband transitions between different wave numbers are excited according to the uncertainty principle; thus, optical near-field can directly excite the carrier in the indirect bandgap. To evaluate the effect of optical near-field confined in a nano-scale, we fabricate the lateral Si p–n junction with Au nanoparticles as sources to generate the field confinement. We observed a 47.0% increase in the photo-sensitivity rate. In addition, by using the thin lateral p–n junction, which eliminates the far-field excitation, we confirmed a 42.3% increase in the photo-sensitivity rate.
Highlights
Silicon is an indispensable material in electric device technology
Because Si is an indirect bandgap material, phonon assistance is required to excite the carriers from the Γ point to the X point in photo-excitation[1,2], which results in a low excitation efficiency while using a propagating far field (FF)
To evaluate the effect of optical near-field (ONF) in photo-excitation, because the size of ONF is in the nano-scale, we fabricated the lateral p-n junction, such that the p–n junction is located at the surface of the device
Summary
Si is an indirect bandgap material; its excitation efficiency, which requires phonon assistance, is low under propagating far-field light. Because Si is an indirect bandgap material, phonon assistance is required to excite the carriers from the Γ point to the X point in photo-excitation[1,2] (refer to Fig. 1a), which results in a low excitation efficiency while using a propagating far field (FF). A direct excitation of Si without phonon assistance is expected to be realized by using the optical near-field (ONF), which is confined in a nano-scale[7,8,9]. Δx Dipole generation of the large wave number from the ONF together with the plasmonic effect, we expected further device improvement. To evaluate the effect of ONF confined in a nano-scale, we fabricated the Si photodetector composed of lateral p–n junction with Au nanoparticles as the ONF source at the p–n junction surface
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