Raman investigation of epitaxial Cu2ZnSnSe4 layers from annealed Sn/Cu/ZnSe(001) precursors on GaAs(001)

We investigate the crystal unit cell orientation of epitaxial Cu₂ZnSnSe₄ films on GaAs(001) using polarized Raman spectroscopy. An epitaxial ZnSe(001) layer is grown in a molecular-beam epitaxy system followed by the deposition of Cu and Sn and annealing in Se atmosphere. This method results in an epitaxially ordered Cu₂ZnSnSe₄ film on GaAs as proven by Electron Backscatter Diffraction (EBSD) measurements and X-ray diffraction. Polarization-dependent Raman spectra of the layers not only exhibit the typical kesterite main modes but also intensity oscillations when the sample is rotated around the optical axis. These oscillations yield information about the orientation of the kesterite crystal unit cell.