Schematic diagram of the photoconductor device pair employed in the photocurrent response measurements. The thickness of the layer is and the etched Si mesa layer is with . One device has nanodots patterned on the surface between the contacts (not shown), while the other device has a smooth unpatterned surface.
Scanning electron micrographs of (a) periodic and (b) random nanodots patterned on SOI photoconductor surface by electron beam lithography.
Measured photocurrent enhancement of SOI photoconducter due to (a) periodically patterned nanodots and (b) randomly patterned nanodots.
One-quarter model geometry employed in the electromagnetic plane wave scattering simulation of a nanodot array on top of a SOI waveguiding layer, approximating the periodically patterned nanodot array on SOI experiment. A harmonic plane wave excitation, , is injected into the simulation volume through the top boundary.
(a) Simulated electric field amplitude squared, , integrated over the Si thin film region of Fig. 4 normalized to integrated over the same region in the absence of the nanodot array. The peak structures in the wavelength range are labeled according to the mode identification of Table I. (b) Calculated absorption enhancement due to randomly distributed dipole oscillators on SOI.
Dispersion curves ( vs ) where is in units of of the various TM and TE modes of the SOI structure plotted in a reduced zone scheme along the direction (solid) and direction (dash) of the reciprocal lattice space. Each intersection of the dispersion curves with the ordinate axis corresponds to the Bragg condition with and is labeled by the vector .
(a) component of the field normalized to the incident plane wave amplitude obtained from the electromagnetic scattering simulation of nanodot array on SOI at showing the strong response of the TM0(2,0) mode to the incident plane wave excitation. (b) component of the normalized field obtained at . The field distribution clearly shows the strong response of the TE0(1,2) mode.
Table of the calculated energies and wavelengths at which the dispersion curves of the waveguide modes in the bare SOI structure intersects the ordinate axis of Fig. 6.
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