Epitaxial Cu2ZnSnSe4 layers by annealing of Sn/Cu/ZnSe(001) precursors on GaAs(001)

We report on the fabrication of epitaxial Cu2ZnSnSe4 films by a two-step fabrication approach. An epitaxial ZnSe(001) layer on GaAs(001) is grown by molecular-beam epitaxy followed by sequential deposition of Cu and Sn. The Sn/Cu/ZnSe(001) precursor is then thermally annealed in a selenium atmosphere. Raman spectroscopy confirms the presence of the kesterite phase. Electron microscopy shows that the films exhibit monocrystalline regions of several micrometers in size with inclusions of smaller grains with a different chemical composition. The latter is confirmed by electron backscatter diffraction measurements which prove the conservation of the crystal orientation defined by the cubic ZnSe/GaAs(001) precursor structure throughout the whole CZTSe film.