Usually, n-macropore density was determined by SCR (space charge region) width. In this paper, under both constant-voltage and galvanostatic conditions, a markedly positive correlation between pore density and HF concentration was evidenced despite a fixed SCR width on low-doped n-Si; the phenomena observed differ a bit from the results dependent on SCR effects. Based on breakdown mechanism and current-burst-model (CBM), an interpretation was given. Additionally, for a given electrolyte and illumination, the correlation between pore density and etching voltage was also found to be considerably positive: both penetrating and focusing power of field strength was supposed to be the underlying factors. The as-produced macropores could be probably significant due to their high density, fast etch-rate and good controllability. (c) 2007 Elsevier Ltd. All rights reserved.