Correlation between optical properties surface morphology of porous silicon electrodeposited by Fe3+ ion

• Electrodeposition of iron ion into porous silicon (PS).
• The PSF surface shows regular distributions of cracks, leaving isolated and uniform regions.
• The PL peak energy shows an S-shaped behavior for PSF3 and PSF11 samples.
• A competition between localized and delocalized excitons is used to discuss the S-shaped behavior.
• The temperature dependence of PL intensity was explained by the tunneling and dissociation model.

In this paper, we analyze the photoluminescence spectra (PL) of porous silicon (PS) layer which is elaborated by electrochemical etching and passivated by Fe3+ ions (PSF) via current density, electro-deposition and temperature measurements. We observe unusual surface morphology of PSF surface and anomalous emission behavior. The PSF surface shows regular distribution of cracks, leaving isolated regions or “platelets” of nearly uniform thickness. These cracks become more pronounced for high current densities. The temperature dependence of the PL peak energy (EPL) presents anomalous behaviors, i.e., the PL peak energy shows a successive red/blue/redshift (S-shaped behavior) with increasing temperature that we attribute to the existence of strong potential fluctuations induced by the electrochemical etching of PS layers. A competition process between localized and delocalized excitons is used to discuss these PL properties. In this case, the potential confinement plays a key role on the enhancement of PL intensity in PSF. To explain the temperature dependence of the PL intensity, we have proposed a recombination model based on the tunneling and dissociation of excitons.