The 1.1, 0.8 and 0.55–0.60 eV deep bands in detector-grade CdMnTe studied by photoluminescence spectroscopy

We present low-temperature photoluminescence (PL) spectra of Cd0·95Mn0·05Te grown by the Bridgman method. This is a promising material for nuclear detectors. We focus on three deep bands: 1.1, 0.8 and 0.55–0.60 eV. In order to achieve high resistivity in our crystals, essential in detector applications, we confirm the role of a deep intrinsic donor level at 0.8 eV, related to TeCd2+. It can pin the Fermi level in the mid-gap and increase the resistivity value. We suggest two interpretations of the 0.55–0.60 eV PL band origin. It can be connected with the deionization of a deep acceptor, such as Cd2−, or with simultaneous transitions of an electron (1.1 eV) and a hole (0.55–0.60 eV) followed by their recombination. These two energies together give the band gap value for Cd0·95Mn0·05Te at 5 K. The 1.1 eV luminescence in our crystals is related to Te secondary phases, the presence of which we confirm by infra-red microscopy. The correlation between the chemical composition of the crystals (changed by Cd- or Te-excess used in growth process and by post-growth annealing), the resistivity value and the PL results is shown.