Mechanisms by which localized excitations move through a crystal are of great interest in various fields of solid state physics. Such kind of transfer takes place in, e.g., laser, cathodoluminescent and electroluminescent materials.
In this communication we analyze tunneling processes of photo - generated electrons and holes between impurities in Cd_xZn_(1-x)Se:Fe,Cr (x = 0, 0.1, 0.2, 0.3) bulk crystals. To study migration of electrons among donor, iron, chromium, and acceptor after switching off external illumination, changes of electron paramagnetic resonance (EPR) signals of the Fe³⁺ and Cr¹⁺ ions were detected. Measured decay times of the EPR signals at liquid helium temperature were long (τ_d ~ 10³ s). However, decay of the Fe³⁺ signal was a bit faster than decay of the Cr¹⁺ signal. Increase of temperature caused decrease of the measured decay times for both impurities. Observed temperature dependence of τ_d has so called activation character. Energy value determined from such dependence correlates well with thermal ionization energy of donors present in the CdZnSe:Fe,Cr system. Results are compared with previous data of Zakrzewski and Godlewski obtained for ZnS:Cu,Fe,Cr.