Abstract
Incorporating group IV photonic nanostructures within active top-illuminated photonic devices often requires light-transmissive contact schemes. In this context, plasmonic nanoapertures in metallic films can not only be realized using CMOS compatible metals and processes, they can also serve to influence the wavelength-dependent device responsivities. Here, we investigate crescent-shaped nanoapertures in close proximity to Ge-on-Si PIN nanopillar photodetectors both in simulation and experiment. In our geometries, the absorption within the devices is mainly shaped by the absorption characteristics of the vertical semiconductor nanopillar structures (leaky waveguide modes). The plasmonic resonances can be used to influence how incident light couples into the leaky modes within the nanopillars. Our results can serve as a starting point to selectively tune our device geometries for applications in spectroscopy or refractive index sensing.
Highlights
Metal nanostructures that support localized surface plasmons (LSP), i.e. collective excitations of the free electron gas within the nanostructures, enable local electromagnetic field enhancement at the nanoscale[1]
We investigate the interplay of local surface plasmon resonances (LSPR) and photonic modes in a complementary metal oxide semiconductor (CMOS) compatible device, in which a crescent shaped NA within the aluminum contact metallization is formed in proximity to a vertical NP Ge-onSi PIN photodetector (NP-PD, Fig. 1a, b)
In contrast to previous research efforts we focus on a device geometry in which device responsivity is strongly influenced by the interplay of localized plasmonic excitations in the crescent-shaped NA with photonic modes in the NP-PD
Summary
Metal nanostructures that support localized surface plasmons (LSP), i.e. collective excitations of the free electron gas within the nanostructures, enable local electromagnetic field enhancement at the nanoscale[1]. LSPs can be utilized to focus incident light into nanoscale semiconductor volumes In these applications, the subwavelength-sized semiconductor structures themselves can sustain discrete photonic m odes[7,8] at selected excitation wavelengths, so-called “leaky waveguide modes”, which enable spectral filtering of absorbed radiation and can pave the way for future integrated light s ources[9,10]. We investigate the interplay of LSPR and photonic modes in a CMOS compatible device, in which a crescent shaped NA within the aluminum contact metallization is formed in proximity to a vertical NP Ge-onSi PIN photodetector (NP-PD, Fig. 1a, b). We show how the interplay between plasmonic and photonic modes can be tuned by adjusting geometry and material parameters
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