Tailoring Visible-Infrared Light Absorption of $\beta-Ga_{2}O_{3}$ with Pyramid-Based Copper Metasurface

In this study, we have numerically enhanced the absorption of light spanning from the long-wavelength visible to the near-infrared region of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-Ga_{2}O_{3}$</tex>. Although <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-Ga_{2}O_{3}$</tex> is an ul-trawide bandgap material and typically absorbs only high-energy photons, we incorporated pyramid-shaped nanoparticles made of copper, effectively acting as a metasurface. Through optimization of the structure and its arrangement density, we achieved a 50 percent increase in light absorption in the wavelength range of 600 nm to 1000 nm. Notably, not only has the absorption been enhanced in the long-wavelength to near-infrared region, but also a slight improvement is observed in the range of 400 to 600 nm. The correlation between tuning the peak absorption wavelength and absorption band has also been explored. The final optimized geometry of the copper-based pyramid is a base span of 15 to 20 nm and a height of 15 nm. The optimized filling fraction is 40 to 50 percent.