Probing of Free Charge Carriers in Nanostructured Silicon Layers by Attenuated Total Reflectance Technique

Infrared spectroscopy in attenuated total reflection (ATR) mode is used to evaluate the concentration of free charge carriers (electrons) in n-type macroporous silicon (Si) layers formed by metal-assisted chemical etching of crystalline silicon (c-Si) followed by additional doping with phosphorus. The ATR spectra are fitted by considering an effective medium approximation and Drude model, which is modified to describe an additional scattering of the charge carriers on the surface of Si nanocrystals. The electron concentration is of the order of 10(19)cm(-3) and it is slightly dependent on the layer thickness, while the surface scattering of charge carriers increases with layer thickness. The obtained results are discussed in view of possible applications of the ATR method for an express diagnostics of doping efficiency of Si nano- and microstructures for photonic and thermoelectrical applications.