Conduction behavior conversion for Cu-doped ZnS/n-type Si devices with different Cu contents

Currents through Cu-doped ZnS (ZnCuS)/n-type Si structures were studied. The electrical conduction investigations suggest that the carrier transport behavior is governed by the Poole-Frenkel emission for ZnCuS/n-type Si devices having the low Cu concentration. However, the carrier transport behavior is governed by the thermionic emission for ZnCuS/n-type Si devices having the high Cu concentration. The photoluminescence result revealed that sulfur vacancy (VS) is the origin of conduction behavior conversion. It is shown that the increased Cu concentration leads to the reduced formation probability of VS. The dependence of VS on the film composition was identified for providing a guide to control the current transport behavior of ZnCuS/n-type Si devices.