Energy transfer in the electroluminescence of ZnS:Mn and ZnSe:Mn driven by short voltage pulses

Abstract

Time-resolved measurements of the light output have been made for DC electroluminescent devices, namely evaporated thin-film ZnS:Mn structures and Schottky diodes made on n-type ZnS:Mn and ZnSe:Mn. Excitation was by square wave voltage pulses with pulse lengths from 10^-7 s to 10^-2 s. For the devices studied, the emission was predominantly from the internal manganese transition. For long pulse lengths, as for DC, the dominant excitation process was direct impact excitation of manganese. For short pulse lengths other centres, which subsequently transferred energy to manganese centres, were excited with higher efficiency. This process leads to a proportionally much higher light output from manganese than does direct impact excitation. The process saturates at longer pulse lengths.