Study of anodization parameters effects on photoconductivity of porous silicon

We have prepared porous silicon by etching p-type crystalline silicon in different conditions such as: varying electrolyte concentration, current density, and etching time. The primary objective of this research is to develop a scientifically based technique for the measurement of photosensitivity. One such technique involves measuring the photoconductivity of the porous silicon under halogen lamp irradiation. Our photoconductivity measurements agree with photoluminescence measurements in previous work, and demonstrate the direct transition of porous silicon. Varied etching conditions change the peak of photoconductivity from 600 to 520 nm (from 2.13 eV to 2.4 eV) as the porosity of the layer gradually increases, and the photoconductivity band also becomes slightly more intense. The photoconductivity peak shift toward shorter wavelength was interpreted to be the result of band gap widening. We observe two distinct regimes in the time decay of photoconductivity, fast decay and steady state, that arise from the recombination process and electron–hole asymmetry near the Fermi surface. Experimental measurements of photoconductivity give useful information about the band gap, band structure, and variation of transport properties due to the micro-structural porosity created during the etching process.