PHOTOLUMINESCENCE PROPERTIES OF Z-BANDS IN CDTE

We have studied the photoluminescence band shape of the 1.38 eV (Z-ban d) and tile 1.32 eV (Z' band) PL bands in high purity low-temperature- grown n-type bulk polycrystalline CdTe as a function of the excitation power and temperature. Both bands have a nonsymmetrical shape with a gradual decrease on the high-energy side but the variation of the shap e with temperature and excitation power is different for Z- and Z'-ban ds. Both bands have the same temperature quenching activation energy E -T = 35 meV. On the basis of our investigations we assign the 1.32 eV emission to a free-to-bound recombination near dislocations and the 1. 36 eV emission to a DA emission near the same dislocation. Both bands are related to a shallow acceptor E-A = 35 meV (probably Li or Na): wh ose concentration in the bulk is quite low. The Z-band is also related to a deep donor(E-D greater than or equal to 200 meV): probably of in trinsic origin.