Thermo-optic Coefficient of Electrochemically Etched Porous Silicon

Thermo-optic coefficient of electrochemically etched porous silicon layer was measured through temperature-dependent reflectance spectroscopy subjected to temperatures ranging from 302.15K to 594.15K. Porous silicon was fabricated via electrochemical etching of a p-type (100) silicon wafer in an ethanol - HF solution with applied current densities of 2.5mA/cm(2), 5mA/cm(2) and 15mA/cm(2) to form similar to 2 mu m thick pSi layers. Using Cauchy's dispersion equation and Bruggeman's effective medium approximation, refractive index and porosity of the samples were calculated respectively. A Fabry-Perot filter derived from the pSi single layers was also fabricated. Normal incidence reflectance spectroscopy was utilized to characterize the filter at different temperatures. The behavior of light in the multilayered structure under different temperatures was modeled using Transfer Matrix Method. The results show that the experimental data is in good agreement with the simulation model. From the empirical data and the simulation results, optical tuning of the Fabry-Perot filter through temperature can be done.