Self-aligned silicon fins in metallic slits as a platform for planar wavelength-selective nanoscale resonant photodetectors

Krishna C Balram,David A B Miller

doi:10.1364/oe.20.022735

Abstract

We propose and demonstrate a novel nanoscale resonant metal-semiconductor-metal (MSM) photodetector structure based on silicon fins self-aligned to metallic slits. This geometry allows the center wavelength of the photodetector's spectral response to be controlled by the silicon fin width, allowing multiple detectors, each sensitive to a different wavelength, to be fabricated in a single-step process. In addition, the detectors are highly efficient with simulations showing ~67% of the light (λ = 800 nm) incident on the silicon fin being absorbed in a region of thickness ~170 nm whereas the absorption length at the same wavelength is ~10 µm. This approach is promising for the development of multispectral imaging sensors and low-capacitance photodetectors for short-range optical interconnects.

Highlights

IntroductionIf we could fabricate multiple nanoscale photodetectors with separately engineered wavelength sensitivities in a single step planar fabrication process, we would enable many different applications
If we could fabricate multiple nanoscale photodetectors with separately engineered wavelength sensitivities in a single step planar fabrication process, we would enable many different applications. Primary among these are the development of multispectral image sensors [1] spanning the visible and near -IR spectral regions with applications ranging from remote sensing [2] to biology [3], next-generation color filter arrays for digital cameras where each pixel can be designed as a miniature visible spectrometer for accurate color reproduction and compact on-chip spectroscopes for lab-on-a-chip systems [4]
Designing resonators that can be tuned by a single lateral dimension leads to a planar single step fabrication process, reducing complexity and leading to low capacitance devices with potentially very high operating speeds

Summary

Introduction

If we could fabricate multiple nanoscale photodetectors with separately engineered wavelength sensitivities in a single step planar fabrication process, we would enable many different applications. We propose and demonstrate a novel planar approach for fabricating tunable resonator-photodetector combinations where the center wavelength of the photodetector’s spectral response is controlled by a lateral dimension. This approach is promising for designing efficient high-speed low-capacitance nanoscale photodetectors for short-haul data communications applications at 850 nm, a wavelength at which silicon is weakly absorbing. One key idea presented here is that the same metallic structure can be used simultaneously for light confinement, wavelength tuning, and carrier extraction [11] [12] This additional functionality leads to devices that cannot be realized by purely dielectric structures. With the semiconductor industry moving towards 3D FINFET-like device architectures [13], the structures here can be fabricated on the same process platform and promise tight integration between transistors and photodetectors for generation on-chip optical interconnects [14]

Results

Discussion

Conclusion