Colour tunable co-evaporated CdS_xSe_1-x (0 ≤ x ≤ 1) ternary chalcogenide thin films for photodetector applications

Cadmium Sulfoselenide CdS_xSe_1-x (0 ≤ x ≤ 1) films were grown by thermal co-evaporation of source materials, CdS and CdSe, taken in the stoichiometric ratio. Systematic shift in the position of X-ray diffractogram (XRD) peak and optical absorption edge have confirmed the change in structural and optical properties as x varied from 0 to 1. Further, photoluminescence (PL) spectra revealed that ternary system has a minimum defect, which is the basic requirement for device applications. The Raman and X-ray photoelectron spectroscopy (XPS) studies have given concurrent results revealing the chemical states of the ternary samples. Detailed analysis of XPS has shown incorporation of oxygen in minor fraction, which proved to help in improving the photoresponse. Electrical study has shown that the electrical properties can varied by changing the composition. All the samples have exhibited n-type conductivity with carrier concentration in the range 10¹⁴ to 10¹⁵ cm⁻³. Finally, photoresponse study showed that sample with x = 0.2 is best suitable for photodetector, where the device can be operated over entire visible range.