Characterization of CuGaSe/sub 2/ thin films grown by MOCVD

Abstract

CuGaSe/sub 2/ thin films have been grown by metalorganic chemical vapor deposition (MOCVD), from three organometallic precursors. Samples of about 1-2 /spl mu/m thick are codeposited onto Pyrex and Mo-coated soda lime glass. A large range of compositions was investigated and characterized. Stoichiometric CuGaSe/sub 2/ thin films are single-phased and their optical bandgap is about 1.68 eV. The features of the films are presented in relation with their composition. XRD spectra always exhibit a preferential orientation along the [112] plane. Secondary phases have been observed: Cu/sub 2/Se for Cu-rich films, CuGa/sub 3/Se/sub 5/ for Ca-rich films. Observation of the morphology reveals larger polyhedral grains for Cu-rich films becoming platelet-shaped and tilted for Ga-rich compounds. The optical properties are also sensitive to the compositional changes and related to the eventual presence of binary phases. The gap increases with the Ga-content. The CuGa/sub 3/Se/sub 5/, phase exhibit a gap of about 1.85 eV. All the samples have a p-type conductivity.