Ordering and Orientation of Epitaxial CuInS2Films Grown on GaP(001) by Three-Source Evaporation

The analyses on the ordering and orientation of epitaxial CuInS2 thin films on GaP(001) grown by three-source evaporation method at 500 °C are reported here in comparison to the films on Si(001). From the X-ray diffraction and the reflection high energy electron diffraction structural investigations, the improved quality of epitaxial film on GaP is demonstrated. For the In-rich and the stoichiometric CuInS2 films, the coexistence of the spinel CuIn5S8 ordered structure and the Cu–Au ordering of CuInS2 with a- and c-axes orientations normal to the GaP(001) substrate are exhibited. It is shown that the slightly Cu-rich film reveals both a- and c-axes orientations of chalcopyrite and Cu–Au orderings. However, the fairly Cu-rich film show dominant twin-free monocrystalline c-axis orientated Cu–Au ordered structures. The existence of sphalerite ordering is probable in all films. Comparing with the films on Si(001), the absence of the growth with random orientation and unknown phases is noticeable. The decrease of twin structures is also observed.