p-Type Characteristics of Cu-Doped CdS Thin Films

The characteristics of Cu-doped CdS films have been studied. Cu was easily diffused into CdS films when CdS was deposited on a Cu film successively at 200°C. The resistivity of the films increased initially with increasing Cu doping, but decreased for values of the Cu/Cd atomic ratio over about 0.5%. The Seebeck coefficient changed from negative to positive, and the Hall coefficient also changed from negative to positive with increasing Cu doping. I-V characteristics of a cell with a CdS(Cu-doped)/CdS(non-doped) film structure showed rectification. Thus, Cu-doped CdS films show p-type characteristics. It is proposed that the Cu compensates the donor due to S-vacancies, and the conductivity type of the CdS films was converted to p-type.