Formation of p-type CdS thin films by laser-stimulated copper diffusion

A new fabrication technique of p-type CdS thin films by He-Ne laser illumin ation of bilayer Cu-nCdS structures at room temperature was investigated. T he n-type CdS films were obtained by vacuum evaporation in a quasi-closed v olume. X-ray diffraction was used to provide crystalline structure and comp osition data of CdS films and Cu-CdS structures. The band gap of CdS films was estimated from the optical transmission spectra. The hot probe and Hall effect studies were used for the determination of conductivity type and co ncentration of charge carriers in films. The formation of a p-n homojunctio n in CdS films or conversion of the film all over to the p-type, depending on the duration of laser illumination, was shown by I-V characteristics, th e photovoltaic, the hot probe and Hall effect measurements. Analysis of con centration distributions of Cu in CdS films, arising as a result of laser-a ccelerated diffusion, by energy dispersive x-ray spectroscopy gave the effe ctive diffusion coefficient of copper, D = 8 x 10(-12) cm(2) s(-1) at T = 2 5 degrees C.