Carriers Recombination and Space Charge Formation in Detector Grade CdTe Studied by Laser-induced Transient Current Technique, Dual-wavelength Photo-Hall and Photoluminescence Spectroscopy
Abstract
Detector grade n-CdTe was studied in detail by Laser-induced Transient Current Technique (L-TCT), dual wavelength photo-Hall effect spectroscopy (DWPHES) and photoluminescence spectroscopy (PL). In case of L-TCT the profit of the technique was significantly enhanced by the optimization of the setup allowing us the measurement in the dynamical biasing regime where the space charge formation in the detector could be monitored.
The DWPHES setup represents an extension of ordinary photo-Hall effect measurement by the steady excitation on an additional wavelength offering the improved specification of the deep levels (DLs) energies and determination of the DLs positions relatively to band edges. Extensive experimental data were simulated by the Shockley-Read-Hall charge dynamic model developed for this purpose and DLs properties were fitted.
The method was demonstrated on a single sample distinguished by unusual features and the benefit of the complex approach to the detailed understanding of processes in the sample was proven. Three detected DLs with threshold energies Ec-0.62 eV, Ec-0.72 and Ec-1.1 eV were found and their effect on the detector quality was revealed.
Basic DLs properties such as defect concentration and capture cross-sections were deduced and discussed with respect to the detector properties.