Determination of the spatial distribution of deep centers from capacitance measurements of pn junctions

Effects of a spatial distribution of deep centers on the junction capacitance are reported for the first time. It is shown that the spatial distribution of deep centers can be calculated from capacitance data measured by both the capacitance-voltage method and the Copeland method, if their energy level is known or assumed. The theory is examined with the experiment on silicon p+n junctions irradiated with 300-kV protons. The analysis yields a value 0.40 eV below conduction band for the energy level of radiation-induced defects, as well as a distribution of the defects with depth.