Photoemission study and band alignment of the CuInSe₂(001)/CdS heterojunction

The contact formation of thin-film epitaxial CuInSe₂(001) with a physical-vapor-deposited CdS layer is presented in this work. Synchrotron-excited photoelectron spectroscopy was used for this investigation. The epitaxial CuInSe₂ films contain a surface layer of reduced Cu stoichiometry similar to the ordered defect compound CuIn₃Se₅. A valence band offset of 0.79±0.15 eV has been determined for this heterojunction. The comparison to literature data indicates that neither surface orientation nor surface copper content have a major impact on the valence band offset of CuIn₃Se₅, respectively, CuInSe₂ with CdS.