A MATHEMATICAL-MODEL FOR THE INFLUENCE OF DEEP-LEVEL ELECTRONIC STATES ON PHOTOELECTROCHEMICAL IMPEDANCE SPECTROSCOPY .2. ASSESSMENT OF CHARACTERIZATION METHODS BASED ON MOTT-SCHOTTKY THEORY

The impact of the assumptions inherent in using the Mott-Schottky theory to identify deep-level electronic states in semiconductors was assessed by comparison to the results of a less restrictive mathematical model. The model, developed in another paper, treated the transport and recombination reactions involving electrons, holes, and electronic states located within the bandgap. The capacitive component used in standard Mott-Schottky theory was found to be insensitive to bulk electronic states within the bandgap for concentrations significantly less than the doping level. The resistive component measured at low frequencies was much more sensitive to deep-level states and may be used to determine their distribution. For high concentrations of deep-level states, the model results were in agreement with the current practice of attributing changes in the slope of the Mott-Schottky curve to partial ionization of single-energy deep-level states with applied potential. In the absence of frequency dispersion, these changes in slope could be attributed instead to nonuniform dopant distribution.