Enhancing near-infrared light absorption in PtSi thin films for Schottky barrier IR detectors using moth-eye surface structures

Abstract

Si-based Schottky barrier infrared detectors typically use thin (1-10 nm) PtSi or Pd₂Si layers grown on Si substrates as an absorption medium. Herein, we demonstrate the use of sub-wavelength moth-eye (ME) structures on the Si substrate of such detectors to enhance absorption of near infrared (NIR) light in the active PtSi layer to increase detector efficiency. Absorbance enhancement of 70%-200% in the λ=1-2.5 μm range is demonstrated in crystalline PtSi films grown via electron beam evaporation of Pt and subsequent vacuum annealing. Low total reflectance (<10%) was measured for ME films, demonstrating the efficacy of the ME effect. Effective medium approximation calculations show that absorption enhancement at short wavelengths is partially due to forward scattering, which increases the effective optical path length in PtSi. Results also suggest that ME structuring of substrates is a general and low-cost method to enhance absorption in a variety of IR material platforms used for back-illuminated detectors.

Nanosecond Laser Fabrication of Novel Micro-/Nanostructured Metal Surfaces: A Dual-Functional Supersurface Combining Antireflectivity and Superhydrophobic Properties

“…However, when the dimensions of the microstructures are on the same order of magnitude as the wavelength of light, light waves cannot detect their presence . In addition, the surface refractive index gradually changes in the depth direction, reducing reflections caused by sharp changes in refractive index, thereby greatly reducing the reflectivity of the surface and eliminating the “moth-eye effect”. , Only a tiny proportion of the light waves are reflected, giving the surface strong antireflective properties. As shown in Figure d, when the surface has both micro- and nanostructures, the incident mode of light is significantly changed.…”

Antireflection Property and Corrosion Resistance of Black Ceramic Superhydrophobic Coatings on Aluminum Alloy

“…Nanostructures can effectively reduce reflected light waves as compared to a smooth and flat surface where most of incident light will be reflected due to the sharp change of refractive index, resulting in "moth-eye effect". [37,38] For a surface with micro-nano structures, the structure will lead to the coupling of incident light and different light, thereby reducing the reflected light. Besides, the "moth-eye effect" produced by the nano structure will also lead to a reduced reflected light, so that the micro nano structure shows excellent antireflection characteristics, as shown in Figure 8d.…”

External quantum efficiency-enhanced PtSi Schottky-barrier detector utilizing plasmonic ZnO:Al nanoparticles and subwavelength gratings

“…Black silicon and moth-eye structures of PtSi in Refs. [8,9] improved the absorption mainly in the 1-2.5 μm shortwave-infrared wavelength range.…”

“…Additionally, other efficient infrared lighttrapping schemes are required to increase the optical path length within the PtSi layer. These schemes include photonic crystals [5] and porous structures [6,7] , black silicon, and moth-eye light-trapping nanostructures [8][9][10][11] . Photonic crystals and porous structures involving texturing the PtSi active layer usually degrade the electrical performance of PtSi SBD.…”