Fundamental aspects of the semiconductor-solution interface

Abstract

Let us begin with a brief summary of the solid state physics of semiconductors. The electronic properties of solids are determined by their band structure. The electron energy levels are grouped into energy bands separated by regions of forbidden energies, and the filling of the available energy levels with electrons determines whether a material is a metal or an insulator. In the case of semiconductors such as silicon, the intrinsic conductivity of the pure material is very low at room temperature, since the density of mobile carriers created by thermal excitation is small. In most practical applications of semiconductors, the conductivity is extrinsic, i.e. it is determined by the concentration of dopants (electron donors in the case of n-type material and acceptors in the case of p-type material). Doping densities vary over a very wide range from 10¹⁵ to 10¹⁹ cm⁻³.