Simulation of the formation of porous-silicon structures

The formation of porous silicon is investigated by the Monte Carlo method in a model that takes account of the nonuniformity of the charge distribution over the silicon-electrolyte interface, hole diffusion, generation, and recombination processes, and size quantization. The structures obtained in a computer simulation for various doping levels of the crystalline substrate, temperatures, HF concentrations, and anode current densities are presented. Analysis of nanoporous structures shows that the porosity depends on the depth and reveals the presence of a fractal dimensionality on scales of less than 10 nm.