Thermally Stimulated Currents in Si〈P,Au〉: Analysis of Rate Equations

Abstract

Thermally stimulated currents (TSCs) in semiconductors were analyzed theoretically in terms of a single-level model. The rate equations describing TSCs in the single-level model were solved numerically for various process parameters, which made it possible to assess the effect of each parameter on the TSC curve. The effects of physical and instrumental parameters were analyzed: the former characterize the material and cannot be changed during measurements, and the latter can be varied readily during experiment (applied voltage, excitation intensity, etc.). By adjusting the instrumental parameters, one can control the shape of the TSC curve and, eventually, assess the parameters of trap levels. The slow and fast retrapping approximations were examined for an arbitrary heating profile and constant-rate heating followed by isothermal holding until complete detrapping. The effect of excitation wavelength on the TSC in Si〈P,Au〉 was studied. It was shown that, using resonance photoexcitation, one can identify the type (electron or hole) of the traps and evaluate their ionization energy. A new approach to TSC data processing was proposed: cleaning of a higher temperature peak from the lower temperature peak by storing the preilluminated material in the dark at the relaxation temperature of the lower temperature peak. The depths and capture cross sections of three trapping centers in Si〈P,Au〉 were evaluated.