The electrical properties and optical properties of Cu-doped CdS films sintered with flux have been investigated. $CuCl_2$ and $CdCl_2$ were used as the dopant source and flux respectively.
The porosity of sintered CdS films decreased with increasing amount of $CuCl_2$ added. Results showed that the resistivity of CdS films was almostly constant up to 100 ppm of $CuCl_2$ added, but 1000 ppm of led to the sharp increase of resistivity.
The sharp change of resistivity with 1000 ppm of $CuCl_2$ is due to the decrease of carrier concentration. It is considered that the decrease of carrier concentration with 1000 ppm of $CuCl_2$ is attributed to the compensation of Cl with Cu doped during sintering.
Results also showed that optical transmittance decreased with increasing the amount of $CuCl_2$ added, which was due to the increase of Cu acceptor level density. The acceptor impurity levels from copper centers ranging from 0.50 eV to 0.55 eV above top of valence band were observed from spectral response.
