Variation of the characteristics of ZnS:Mn AC thin-film electroluminescent devices with insulators

In pursuing a high bright ZnS:Mn AC thin film EL device with low operating voltage, we find that improvement of the insulator material is an effective way to achieve this goal. The process is illustrated with the devices fabricated with three types of insulator materials: silicon oxynitride (SiON), barium tantalate (BTO) and aluminum/titanium oxide (ATO). The results show that the insulator material affects EL device performance not only via the well known effect of insulator capacitance but also through the modification of the ZnS:Mn/insulator interface properties. Using analytical techniques, such as current vs. field and charge vs. voltage measurements, the properties of the interfaces between ZnS:Mn and BTO, ATO and SiON are deduced. It was found that these interfacial properties varied greatly among the three types of insulator materials investigated. The interface states in BTO devices are deep levels and the concentration of trapped charge at these states is high. On the other hand, the interface states in ATO devices are shallow levels and trap very few charges. Because of the excellent interfacial properties, the BTO devices exhibit the highest brightness and luminous efficiency of the three kinds of EL devices investigated.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.