ZnS-like Behaviour of Efficient CaS:Eu Electroluminescent Devices

Abstract

The mechanism of high field a.c. driven electroluminescence (EL) in MISIM structures (M-etal, I-nsulator, S-emiconductor) is rather well-understood in the case of S = ZnS:Mn [1, 2, 3, 4, 5]. Operation of these devices comprise as the main processes the tunnel emission of electrons from the interfaces between the I- and the S-films only at fields above the ballistic acceleration threshold, the ballistic accceleration of these electrons, their multiplication after reaching kinetic energies of about 7eV, and of course the direct impact excitation of Mn²⁺. One important prerequisite of the first mentioned process is the existence of deep enough interface states of appropriate density (IF-DOS) [eV^-1cm^-2], into which the multiplied electrons are trapped after reaching the momentary anode, before the polarization field surges them back into the bulk after the end of the applied field pulse.