On the Excitation Mechanism of the Thin Film Electroluminescence of ZnS; Cu, Mn, Cl

Thin film of ZnS; Cu, Mn, Cl prepared by direct vacuum evaporation shows an orange-yellow emission when a negative pulse voltage is impressed on the aluminium electrode. The relation between the impressed voltage V and the emission intensity B deviates evidently from the well-known formula ln B 1/√V if the range of the voltage is wide. On the basis of the measured V-I characteristics and the observed current waveform, it is apparent that electron avalanche takes place due to collision ionization in the thin film. From this point of view, supposing the model that electron avalanche by collision ionization takes place inside the so-called Schottky barrier of the Al-ZnS contact and these electrons excite Mn luminescent centers, a calculated curve is obtained with a simple model and this agreed very closely with the typical experimental data of the emission characteristics.