It is difficult to produce nice macropores at high speed with strong oxidants via the breakdown mechanism on low doped n-Si. In this letter, HF-containing electrolytes were modified with strong oxidants; galvanostatically anodizing in the dark, macropores with depths upto 80 mu m and pore-diameters between 100 and 1000 nm were fast produced on low doped substrate. Two new phenomena were observed: pore tips could be tumefied simultaneously and macropores could be filled with a uniform microporous layer under dark conditions. Mild short-range ordering of pores was observed. The macropores are rather nice while the etching rate could reach the highest of its kind, 1800 mu m/h. The underlying mechanism was in the framework of the current-burst-model combined with avalanche breakdown; both pore pitch and pore-wall thickness could be significantly less than SCR (space charge region) width. Published by Elsevier Ltd.