Morphological and optical properties of n-type porous silicon: Effect of etching current density

Abstract

Morphological and optical properties of porous silicon (PS) layer fabricated on n-type silicon wafer have been reported in the present article. Method of PS fabrication is by photo-assisted electrochemical etching with different etching current densities (J). Porosity and PS layer thickness, obtained by the gravimetric method, increase with increasing J. Pore morphology observed by FESEM shows the presence of randomly distributed pores with mostly spherical shape. Calculated pore size is also seen to increase with increasing value of J. XRD gives the characteristic amorphous peak of PS along with some peaks corresponding to crystalline silicon (c-Si). Calculated crystallite size shows decreasing trend with increasing J value. The optical properties of these samples have been investigated by UV-visible reflectance, Raman spectroscopy and photoluminescence (PL) spectra. Reflectance measurement shows blue-shift of the spectrum with increased reflectivity for increasing J. Raman spectra show remarkable blue-shift with respect to the c-Si peak. PL spectra give the luminescence energy in the orange-red region of the visible spectrum and little change with variation of J.