Characterization of CuIn(Ga)Se2 Thin Films

Abstract

Cu-rich and nearly stoichiometric CuIn(Ga)Se2 thin films prepared by the rapid thermal process (RTP) are investigated by electrical and optical methods. The experiments yield that three phases are present in the layers. Cu2—xSe, which determines the conductivity of the layers but does not contribute to the radiative recombinations is observed. CuIn1—xGaxSe2 causes a broad unstructured radiative recombination with a peak energy in the range from 1.0 to 1.1 eV, dependent on x. Recombinations with zero-phonon lines at 0.96 and 0.90 eV arise from CuInSe2. They involve a shallow donor with a binding energy of (10 ± 5) meV and two acceptors with binding energies of (75 ± 10) meV and (140 ± 10) meV, respectively. All features of these recombinations are well described in the donor–acceptor pair recombination model.