Comparison of CdS/CdTe superstrate and substrate devices fabricated with a ZnTe:Cu contact interface

Superstrate and substrate CdS/CdTe devices have been fabricated with a ZnTe:Cu contact. The main variable probed is the effect of Cu diffusion from the ZnTe:Cu contact interface layer. A combination of electrical and composition analysis indicates that, for the substrate devices produced for this study, the amount of Cu in the CdTe layer is too high for optimum device operation. Admittance spectroscopy analysis suggests that superstrate devices with excessive Cu have similar defect functionality as the substrate devices with a ZnTe:Cu contact interface. Temperature-dependant, current-voltage analysis further suggests that it may be possible to ascribe subtle differences in I-V rollover to either a back-contact barrier or an artifact of Cu in the CdS.