A mathematical model for identification of deep level electronic defects in semiconductors by photoelectrochemical A.C. impedance spectroscopy

novel method is proposed for the characterization of deep-level defects in n-GaAs. This method is compared to traditional Mott-Schottky based techniques. This work was conducted by simulating the A.C. impedance response of an ideally-polarizable n-GaAs semiconducting electrode using a transport-based mathematical model. The model involved solution of the steady- and sinusoidal-steady-state expressions for the material balances for each species coupled with expressions to account for changes in the electrostatic potential throughout the system. These solutions were valid for an n-type, ideally-polarizable semiconductor with an arbitrarily chosen distribution of interband states at a specific energy level. The experimental conditions simulated would be readily accessible using a simple experimental apparatus consisting of standard A.C. impedance instrumentation and a light source capable of providing sub-bandgap illumination.;Deep-level species were found to exhibit a strong influence on the real portion of the impedance, while the imaginary portion, on which Mott-Schottky theory is based, was found to be relatively insensitive to these species. A new highly sensitive method is proposed which would take this information into consideration. This analysis would give the experimentalist the ability to calculate the energy level, concentration, and spatial distribution of these species through application of Mott-Schottky analysis, real impedance studies, and use of asymptotic expressions for the components of an equivalent electrical circuit.;The study indicated that Mott-Schottky analysis provides excellent characterization of the doping level and flatband potential for a uniformly doped sample with a low concentration of interband states. Related...