Influence of fabrication parameter on the nanostructure and photoluminescence of highly doped p-porous silicon

Porous silicon (PS) was prepared by anodizing highly doped p-type silicon in the solution of H2O/ethanol/HF. The effects of key fabrication parameters (HF concentration, etching time and current density) on the nanostructure of PS were carefully investigated by AFM, SEM and TEM characterization. According to the experimental results, a more full-fledged model was developed to explain the crack behaviors on PS surface. The photoluminescence (PL) of resulting PS was studied by a fluorescence spectrophotometer and the results show that PL peak positions shift to shorter wavelength with the increasing current density, anodisation time and dilution of electrolyte. The PL spectra blue shift of the sample with higher porosity is confirmed by HRTEM results that the higher porosity results in smaller Si nanocrystals. A linear model (λPL/nm=620.3-0.595P, R=0.905) was established to describe the correlation between PL peak positions and porosity of PS.