Spectral shifts of electroluminescence from porous n-Si under cathodic bias

Abstract

Spectral shifts of visible electroluminescence (EL) from cathodically biased n-Si in electrolyte solution containing persulfate ions are described. The electrochemically etched n-Si cathodes exhibit a blue shift of the EL with the increase of applied potential. It is explained that the blue shift is caused by the formation of an accumulation layer and the Fermi level pinning in the porous Si. A study of the EL as a function of time at a constant potential shows a red shift, which can be attributed to the bandgap lowering caused by the conversion of the predominant surface bonds Si-H to Si-Si. Electropolymerization of aniline on the porous Si surface enhanced the stability of the EL possibly due to the strengthening of the surface bonds.