Broadband MIR harvester using silicon nanostructures

In this work, we propose an all-silicon-based super absorber in the mid infrared (MIR) spectral range. The presented structures are composed of n-doped silicon nanoparticles or nanowires embedded in intrinsic silicon. An intense absorption peak is observed and could be tuned across the MIR range. While nanoparticles give a single broad absorption peak, the nanowires structure shows a broadband absorption of more than 70% from λ = 5 to 13 µm reaching up to 99% at 7 µm. The absorption peak could be extended to more than 20 µm by increasing the length of the nanowire. Increasing the diameter of the nanoparticles gives higher absorption, reaching just above 90% efficiency at λ = 11 µm for a diameter of 1500 nm. Changing the geometrical parameters of each structure is thoroughly studied and analyzed to obtain highest absorption in MIR. The proposed structures are CMOS compatible, have small footprints and could be integrated for on-chip applications.