Growth mechanism and the properties of CIGS thin films for zero bias photodetector devices

Abstract

CuInGaSe2 quaternary thin films have been deposited using a single-source, single-step thermal evaporation technique using hydrothermally fabricated CIGS powder. Highly crystalline, homogeneous, and stoichiometric CIGS powder source was prepared by a hydrothermal method and then evaporated at substrate temperatures of room temperature, 150°C, and 300°C. The bulk and surface structural, morphological, and optical properties of the samples were analyzed. The sample deposited at room temperature did not show any phase formation; however, increasing the substrate temperature resulted in the formation of binary and quaternary phases due to interdiffusion of the species. XPS and Raman spectra analysis revealed nanocrystalline Cu2Se phase formation at the interface, while the bulk of the sample remained single-phase CIGS. A higher deposition temperature also facilitated larger grain size and a more compact surface morphology. Increasing the substrate temperature increased the likelihood of interdiffusion of the species from the evaporation flux and controlled the bulk and surface properties of the samples. CIGS/CdS active photodetectors were fabricated by deposition of a CdS buffer layer, with the sample deposited at 150°C showing the highest photocurrent along with low response and recovery times at 0 V bias.