Stresses caused by Cd and Te inclusions in CdMnTe crystals and their impact on charge carrier transport

Abstract

We present a defect analysis in Cd and Te inclusion regions within Bridgman-grown Cd0.95Mn0.05Te crystals for nuclear detectors. Crystal growth was performed under Cd- or Te-rich conditions so that Cd and Te inclusions could be investigated, respectively. Cathodoluminescence (CL) maps confirm that a Te inclusion does not generate defects in its vicinity, in contrary to a Cd inclusion, which induces microcracks in its neighborhood in the CdMnTe matrix. This originates from the higher thermal expansion coefficient ratio of Cd to the CdTe than Te to CdTe. Next, the relative stress analysis was carried out using the electron backscatter diffraction (EBSD) technique, which shows that a Te inclusion causes higher stresses in its environment than a Cd inclusion does. The reason for this is that the Cd inclusion releases the stresses due to a creation of the tensile cracks. Despite the fact that a Te inclusion stresses the crystal lattice more, it can have a smaller impact on charge carrier transport in nuclear detectors than a Cd inclusion. This effect we confirm by μτ product measurements, which determine charge carrier transport properties.