The Edge Emission in CdS Crystals

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Abstract
In this paper the mechanism of the green edge emission in pure, undoped CdS crystals is investigated. First, a systematic study of photoconductive, transport and luminescent properties and their dependence on heat treatment (350 °C) has been carried out. The photoconductive measurements between 77 and 130 °K indicate that a class II centre (Sp ≫ Sn) lies 0.13 to 0.15 eV above the valence band. The experimental results are then compared with calculations based on a three centre model and carried out by electronic computer over a range of temperatures and centre densities. The observed luminescent properties can be predicted in agreement with experiment, but only if the radiative recombination takes place between a free electron and a hole trapped in the above centre (Schön‐Klasens model). The effect of heat treatment and the nature of these centres are briefly discussed.