Study of growth of dot and column in porous silicon samples of various thicknesses prepared at a constant current density

Abstract

Porous silicon is considered to be composed either of spherical shaped interconnected silicon quantum dots or combination of quantum dots and columns. This paper presents a study of a series of porous silicon films of various thicknesses, prepared at a 20mA current density by the electrochemical etching technique. The photoluminescence spectra of the series samples were monitored. Further, we used a photoluminescence fitting model by Singh and John (John–Singh) in its extended form by Elhouichet to estimate the percentage of dots and columns; their average diameters and corresponding variances. The shape of experimental photoluminescence spectra fits well with John–Singh model. As a result, the analytical curves drawn using the fitting parameters showed the decrease in mean crystallite diameter of columns and dot while increase in variance of column and decrease in variance of dots. Hence, more homogenous dots are formed. Thus, it results in the formation of a more ordered nanocrystalline structure with more porosity. It verified the quantum assumptions. The discrepancy in the PL behavior of a sample is well explained by the model.