Self-compensation in semiconductors

The problem of self-compensation of charged dopants is analyzed. Special em phasis is given to dopants in binary oxides. It is shown that one can deter mine the degree of self-compensation from the properties of the host materi al and dopant concentration alone. It is further shown that for a native p- type semiconductor, donors are compensated, mostly, by native ionic defects . On the other hand, doping with accepters allows us to increase significan tly the hole concentration, i.e., self-compensation is low under high dopin g levels. For a native n-type semiconductor the opposite is true, namely, e xtrinsic accepters are mainly compensated by native ionic defects. It is sh own that the changes in concentration of all the charged defects are simply related by a single factor, the doping factor f, or its power f(k) where k depends solely on the defect's charge. Quantitative calculations off and d efect concentrations are presented for Cu2O, which was used as a model mate rial. It is found that for p-type Cu2O doping with donors results in f with in the range of 1-10, depending on the dopant concentration and P(O-2). Thi s means that the hole concentration decreases and the electron concentratio n increases at most by a factor of 10. Therefore one does not expect to obt ain a changeover from p- to n-type cuprous oxide by doping, under equilibri um conditions. Most of the donors are compensated by negative ionic defects . Self-compensation in the presence of amphoteric defects and Fermi level s tabilization are discussed, using the former formalism. [S0163-1829(99)1133 5-3].