Optical properties modulation of porous silicon layers for optoelectronics applications

Abstract

Refractive index of porous silicon (PS) were modulated throughout the chemical oxidation, thermal oxidation and controlling current density during PS formation. The oxidized PS layers showed a good gradient of refractive index to application in waveguide devices, with higher refractive index in sub layer near de surface and less refractive index close to PS/Substrate interface. In order to fabricate wave guide devices, Silicon wall were formed of 10 to 20 micrometer wide, 10 micrometer high and 1000 micrometer to 10000 micrometer length. Wall formation were achieved throughout anisotropic etching process in 7M KOH aqueous solution at 75 degrees Celsius. The properties of PS layer were analyzed by Raman spectroscopy, Infrared spectroscopy (FTIR), optical and scanning electron microscopy and reflectance spectroscopy. PS multilayers on the walls, as well as on the substrate, are formed by means of a chemical anodization process with various current densities. The structures are characterized using scanning electron microscopy, optical imaging, and Raman spectroscopy. Raman analysis shows a multilayer structure on the walls, suggesting different refractive indices for each layer. These results indicate the possibility of obtention of visible light waveguides formed by porous silicon multilayers made on silicon vertical walls.