Mechanism of the Green-Copper Luminescence in ZnS Crystals. I. Direct Evidence for the Pair Emission Mechanism

Abstract

Using a ZnS:Cu, Al crystal grown from the melt, precise measurements were made at liquid helium temperature on the relationship between the decay rate of the green-copper luminescence and those of two kinds of photoinduced absorptions, one due to holes created at copper acceptors, and the other due to electrons trapped at aluminum donors. It was found that the decay rates of the two kinds of absorptions are equal to each other, and are about one half of that of the luminescence. This fact clearly incicates that the green-copper luminescence is caused by the recombination of electrons trapped at aluminum donors with holes trapped at copper acceptors according to the bimolecular kinetics, and provides the direct experimental evidence for the conclusion of the donor-acceptor pair emission mechanism for this luminescence presented in the previous investigations.