The structural and optical properties of high-purity undoped semi-insulating crystals, grown using physical vapour transport and modified vertical Bridgman techniques, were studied. The samples were prepared from 7N-purity source elements via direct synthesis, followed by heat treatment to adjust the stoichiometry. Experimental measurements were systematically performed by using cathodoluminescence and high-resolution X-ray diffraction techniques; before and after annealing. The cathodoluminescence emissions from low- and high-resistivity samples were studied in order to relate the cathodoluminescence bands to the presence and concentration of native defects. Two broad luminescence bands were found, in addition to the expected emission which was related to excitonic recombination. The natures of the defects which were involved in the transitions were studied by analyzing the positions of the energy levels and the relative intensity variations of the cathodoluminescence peaks.

Crystal Defects and Optical Transitions in High Purity, High Resistivity CdTe for Device Applications. N.Armani, C.Ferrari, G.Salviati, F.Bissoli, M.Zha, L.Zanotti: Materials Science and Engineering B, 2002, 91-92, 353-7