Optical and electrical characterisation of iron-doped ZnO

The 1.7855 eV luminescence and electrical DC behaviour in polycrystalline ZnO are studied. Luminescence transient decay times of 1.4 ms and 23 ms are found at 11 K. While the first one remains constant with temperature the slower one decreases reaching a value of 5 ms at 160 K with an activation energy of 76 meV. A fast decrease of the intensity above 30 K with activation energy of 8 meV was found. Electrical DC measurements show a space charge limited current behaviour with an activation energy of 40 meV above 30 K. For lower temperatures a variable range hopping was found. Based on this data an excitonic model for the centre is proposed.