Four-probe technique electrical resistivity distribution over textured specimen surface: (a) initial textured surface, ρav = 2±0.13 Ohm×cm; (b) surface with porous layer formed in 5 min, ρav = 3.2±0.11 Ohm×cm; (c) same with 10 min etched porous silicon layer, ρav = 2.13±0.09 Ohm×cm; (d) same with 15 min etched porous silicon layer, ρav = 3.1±0.5 Ohm×cm.