Low mechanical pressure during electrochemical etching: induced modification in optical and structural properties of n-type porous silicon

In this study, n-type porous silicon (PS) layers are formed in the dark with the assistance of a low mechanical pressure during electrochemical etching process. Pressure-induced stress/strain modifies the resistivity of the silicon substrate to enhance the etching process. Under the same equivalent etching condition, pressure-assisted etching can yield PS layer with stronger room temperature photoluminescence intensity than the layer formed by ordinary electrochemical etching. The porosity of pressure-assisted etched PS layers is found to be much higher than that of ordinary etched layer. Fourier transformation infrared absorption spectroscopy and grazing incidence X-ray diffraction measurements and analysis show that application of the pressure during electrochemical etching promotes the degree of oxidation and reduces the crystallites size of the PS layer. The effect of the pressure during etching process on the surface topography of PS is revealed by scanning electron microscopy imaging.