Optical characteristics of porous silicon photonic crystals prepared on the back surface of silicon wafers

摘要

Surface-enhanced Raman scattering sensors and optical detection devices often incorporate rough surfaces or porous Si photonic crystals to enhance optical absorption and localized surface plasmon resonances. This study reports a porous Si photonic crystal structure fabricated on the backside of a crystalline Si substrate by room-temperature electrochemical etching. Scanning electron microscopy showed that the rough surface did not affect the vertical etching rate, but influenced the porosity and pore size distribution. X-ray diffraction analysis showed broader and lower-intensity peaks from the sample prepared on the back side, indicating that the backside porous Si had strong light-scattering effects and lattice contraction, which led to greater oxidation because of its higher porosity. A reflectance of ~1% was obtained over a broad wavelength range (400-700 nm) and the optical reflectance suppression mechanism was analyzed. These optical characteristics showed backside porous Si photonic crystals have significant potential utility in photovoltaic and photonics applications.