Charge Exchange Mechanism Responsible for P‐Type Silicon Dissolution during Porous Silicon Formation

Abstract

The anodic current‐voltage characteristics of P silicon which are obtained in electrolyte in the conditions corresponding to porous layer formation are studied in detail and analyzed according to an elementary model which accounts for the depletion layer at the silicon surface and the Helmholtz layer in the electrolyte. It is found that the determining step of silicon dissolution is the charge exchange from the bulk silicon to the semiconductor surface. This process occurs through a thermionic emission mechanism over the Schottky barrier which is formed at the silicon surface, whenever the doping level is from . Variations in the silicon doping concentration provoke a potential shift in the current‐voltage characteristics, which is almost proportional to the square root of , and which explains the selectivity of porous silicon formation vis‐a‐vis the doping level of silicon.