ABSTRACT
In order to prepare device quality crystals, it is important to control the defect population precisely. Electrons dominate the electronic defect population and the compound will be an n-type semiconductor. This chapter shows that the number of defects in a material and its electronic conductivity can be quite easily understood from the same viewpoint. It looks at how the stability of an oxide depends on the oxygen pressure. The pressure dependence of conductivity was precisely that expected from the defect model used. Many of the important semiconducting materials show composition ranges which take them from cation deficient to cation excess. At the same time the semiconductivity often changes from p-type to n-type or vice versa. From a practical point of view, it would be helpful to be able see how the conductivity will change with composition at a glance without always having to return to chemical equilibrium equations.
