Influence of Etching Current Density on Visible Electroluminescence from Porous n‐Si under Cathodic Bias

Abstract

Visible electroluminescence (EL) from cathodically biased n-Si in an electrolyte solution containing S 2 O 8 2Ϫ has been studied. EL from the porous n-Si samples fabricated by photoelectrochemical etching over a wide range of current densities (J a ) shows both blueshift and peak broadening with increasing J a , which can be attributed to the progressive participation of more silicon hydride species, Si-H n , with larger n in the emitting progress. Based on analysis of spectral changes and resolution of the EL peak into components, a revised mechanism of the EL, where silicon hydrides are considered to donate electrons to sulfate radical anions, is proposed. EL is produced by recombination of the resulting radical, Si-H n• ϩ , with an accumulated electron in the conduction band. The radicals would lead to competing reactions that strip off hydrogens from the surface silicon hydrides. Si-H n with larger n is subject to the earlier EL.

Effect of Surface Modifications on Spectral Shift of Electroluminescence of Porous n-Si in S[sub 2]O[sub 8]2−] under Cathodic Bias

“…porous Si surface, as reported by Tsai et al, 14 and the discussion from a kinetic viewpoint by Park et al 26…”

“…Since it is difficult to explain the spectral shifts in terms of the size changes of the silicon nanostructures, we interpret the spectral shifts by using a recently proposed mechanism involving silicon hydrides. 26 The spectral shift is linked to the change in the energy levels of silicon hydrides and of accumulated electrons in the conduction band of the porous Si. Complementary information from transmission FTIR spectroscopy regarding the chemical composition of the surface provided important insight into the mechanism controlling the EL.…”