Theory of Deep Level Spectroscopy in Semi-Insulating CdTe

Numerical simulations of thermoelectric effect spectroscopy (TEES) and photo-induced transient current spectroscopy (PICTS) in CdTe were performed with the aim to interpret experimental results and to look for possibilities to obtain credible information about trap capture cross-sections. The TEES and PICTS spectra were calculated by solving kinetic equations. Trap energy and capture cross section were determined by variable heating rate and double gate methods and compared with input data. Deviation of the established capture cross-section from the input value was demonstrated for the strong retrapping. It was concluded that the trap capture cross-section, especially if obtained anomalously low, might be incorrect due to invalid premises of models, which neglect retrapping. The possibility to acquire an information about trap properties from the shape or magnitude of glow curves was checked. It was demonstrated that the magnitude of TEES signal corresponding to slow or fast retrapping depends unequally on the initial optical excitation.