ON THE ELECTRICAL-IMPEDANCE DUE TO THE ANODIC-DISSOLUTION OF SILICON IN HF SOLUTIONS

The electrical impedance measured at p-type and highly doped n-type Si electrodes in HF solutions in the potential range of pore formation h as been interpreted using a basic model. This model includes two elect rochemical reactions (hole capture and electron injection) followed by a chemical oxidation reaction, and accounts for the main results repo rted in the literature. The electrical impedance has been calculated f or the anodic dissolution proceeding both under depletion-layer and He lmholtz-layer control. It has been concluded that the impedance and, i n particular, the inductive loop measured in the onset region of the a nodic dissolution can be explained fairly well on the basis of the mod el and assuming depletion layer control. The inductive loop is ascribe d to electron injection from a surface intermediate of the dissolution process into the conduction band.