Origins of the enhanced broadband absorption in black silicon

Although black silicon is utilized in a wide range of applications due to its broadband spectral emission and absorption, the underlying electromagnetic mechanisms are not well explored. In this study, the underlying phenomena that are responsible for these enhanced spectral features are investigated. The absorption spectra of the black silicon with random textures are analyzed, and the electromagnetic mechanisms that drive elevated absorption are explored. Our findings reveal that two separate electromagnetic phenomena occur in the textures, effective wavelength matching and waveguide modes. Detailed analysis reveals that the occurrence condition of those phenomena is highly dependent on the dimensions of the textures in the transverse direction. The effect of the texture dimensions and doping concentration both on absorption characteristics and physical phenomena is analyzed in detail. The findings of this study explain the absorption mechanisms of black silicon observed in experimental studies, which can lead to designer materials with rough surfaces for the desired spectral emissivity.