Investigation on the Effect of Direct Current and Integrated Pulsed Electrochemical Etching of n-Type (100) Silicon

This paper investigates the effects of different etching techniques between direct current electrochemical etching (DCPEC) and integrated pulsed electrochemical etching (iPEC) on the structural and optical characteristics of porous silicon formation.The n-type Si (100) was fabricated using both techniques in an electrolyte that consists of aqueous hydrofluoric acid (HF) and ethanol (C2H5OH) with a ratio of 1:4.An additional pulse cycle of 14 ms with Ton = 10 ms and T off = 4 ms was supplied for iPEC porous silicon sample.The finding from both samples showed that the pore formation was affected by the etching techniques used.The porous silicon etched by the DCPEC technique produced a square-like pore with a porosity of 40% while the iPEC technique formed a mix of square and crossed shape pore with a porosity of 52%.From atomic force microscopy, the sample prepared by DCPEC was identified to have a deeper pore that causes larger crystallite size and better intensity in the Raman and photoluminescence spectra.On the other hand, the iPEC technique produced a higher and larger value of surface porosity and pore diameter but it has a shallower pore.The photoluminescence peak corresponding to red emission (S-band) is observed at 642 and 637 nm for DCPEC and iPEC samples, respectively.This is due to the nanoscaled size of silicon through the quantum confinement effect that was estimated to be around 7.9 nm and 7.8 nm for DCPEC and iPEC samples, respectively, determined from the quantized state effective mass theory.