Abstract:
The electrical conduction process through CdS thin films prepared by the chemical bath deposition technique was studied in six different device structures, i.e., Au/CdS/Au, Au/CdS/ZnO(Al), Mo/CdS/Au, Mo/CdS/ZnO(Al), Cu(In,Ga)Se2/CdS/Au and Cu(In,Ga)Se2/CdS/ZnO(Al). The results of I-V characteristic measurements of these structures at room temperature indicated that the electrical conduction process through CdS thin films and related junctions of the structures Au/CdS/Au, Au/CdS/ZnO(Al) and Mo/CdS/Au are ohmic and those of Mo/CdS/ZnO(Al) are both ohmic and non-ohmic. The I-V characteristics of Cu(In,Ga)Se2/CdS/Au and Cu(In,Ga)Se2/cdS/ZnO(Al) are obviously rectifying type or diode characteristics. From the I-V analysis of these structures it was also concluded that the electrical conduction process through CdS thin films measured across the plane is ohmic, as is that of the Au/CdS junction, whereas those of Mo/CdS and CdS/ZnO(Al) are of non-ohmic type and those of Cu(In,Ga)Se2/CdS are of rectifying type. The resulting analysis can be used to draw the energy band diagram for structures consisting of CdS and related junctions. The CdS thin film resistance measured across the films is in the range of 10x10-10x10x10 ohm-cm whereas that measured inthe plane of the films is approximately 10x10x10x10x10x10 ohm-cm. The properties of CdS thin films depend greatly on parameters used in the deposition process.