Spectroscopic cathodoluminescence studies of the ZnTe:Cu contact process for CdS/CdTe solar cells

Spectroscopic cathodoluminescence (CL), electron-beam induced current (EBIC), and capacitance-voltage (C-V) measurements are used to study the formation of CdS/CdTe devices processed using ion-beam milling and a ZnTe:Cu/Ti contact. Results show heating in vacuum at ∼360°C and ion-beam milling lead to observable changes in the CL emission from the CdCl₂-treated CdTe surface. Changes in the CL spectrum are also observed as ZnTe:Cu layer thickness increases. These changes are correlated to published studies of defect levels and shown to be due, possibly, to an n-type region existing between the ZnTe:Cu contact interface and the p-CdTe layers. This n-type region is eliminated once a sufficiently thick ZnTe:Cu layer is produced.