Control of the porous structure of n-type silicon and its electroluminescence properties

During the galvanostatic preparation of n-type porous silicon samples, the saturated photocurrent density was found to be the key factor determining the structure of the porous layer, which was either a homogeneously nanoporous monolayer or a double layer consisting of a nanoporous top layer and a macroporous underlayer. The electroluminescence (EL) properties of two different samples with the different layer structures showed a difference in the peak wavelength range of the spectral dependence on negative bias. The EL spectra from the samples with the double layer structure were observed over a larger spectral range than that of the samples with the monolayer structure. These results suggest that the luminescence wavelength range of n-type porous silicon can be changed by adjusting the saturated photocurrent density during anodization. Furthermore, an attempt was made to explain the blue-shift phenomenon of the EL wavelength with an increase in applied negative bias, on the basis of the correlation between the porous layer structure and the luminescence wavelength.