Anodic Behavior - Electrochemistry of Silicon and Its Oxide - page 168

5.2.1. Fluoride Solutions
The i-V curves, as shown in Fig. 5.2, are different for p -Si and n -Si in the dark
due to the difference in the concentrations of holes, which are required for the anodic
reactions, in the two types of materials. 73 Large currents can be obtained on p- Si by
anodic polarization which gives a forward bias to increase the concentration of holes
at the surface. On the other hand, for nondegenerated n -Si the anodic current is limited
by the availability of holes. The i-V curve for n-Si becomes identical to that for p -Si
when n -Si is illuminated at a sufficiently high light intensity.
The anodic polarization curves of p- Si or strongly illuminated n -Si in fluoride
solutions are typically characterized by two peak currents, and and two plateau
currents, and as shown in Fig. 5.2. At anodic potentials up to that at the elec-
trode behavior is characterized by an exponential dependence of current on potential
and by the uneven dissolution of silicon surface leading to the formation of porous