ELECTRON EJECTION PROCESSES AT INSULATOR-SEMICONDUCTOR INTERFACES IN ACTFEL DISPLAY DEVICES

Luminance, conduction current and threshold voltage of ZnS:Mn ac thin film electroluminescent display devices were measured as functions of device temperature (10 K-300 K) and risetime of the excitation voltage pulse (2 mu s-50 mu s). Results provided insight into the electron ej ection mechanism at the insulator-phosphor interfaces. It was found th at the distribution of interface state electrons at the beginning of t he excitation voltage pulse varied substantially with device temperatu re. Pure tunneling is thought to be the dominant electron ejection mec hanism at the beginning of the voltage pulse while phonon-assisted tun neling is responsible for altering the interface electron distribution during the interval between the pulses. A delay of several microsecon ds was observed in the build up of the transferred charge. It is attri buted to the relatively small population of electrons available at the insulator-phosphor interface.