Effects of etching time on the morphology of porous silicon structure formed by potential-assisted electrochemical etching

Several parameters such as doping concentration and crystal orientation of the substrate, electrolyte composition, applied current density and etching time play an important role in the electrochemistry of silicon [1–4]. However, illumination is another major parameter in Si etching process, particularly for n-type material [5]. In this paper, porous silicon (PS) structures were prepared under front-side illumination of UV light (12 W) at various etching times. The evolution of pore structures as a function of etching time has been investigated. The fabricated PS samples show clear four-branching structure suggesting that etching enhances in <001> and <010> directions faster than <100> direction. This pore deformation can be described by the proposed three consecutive phases based on the current burst model [6–7].