CuAlSe₂ chalcopyrite epitaxial layers grown by low-pressure metalorganic chemical vapor deposition

Epitaxial layers of CuAlSe₂ chalcopyrite crystals were successfully grown on GaAs and GaP substrates by low-pressure metalorganic chemical vapor deposition. The epilayers were comprehensively characterized by X-ray diffraction, transmission electron microscope, transmission electron diffraction, electron-probe microanalysis, secondary-ion mass spectrometry, photoreflectance (PR), photoluminescence (PL), and Hall measurements. Dependence of growth rate and film properties on growth parameters, such as growth temperature and input molar flow ratio of the metalorganic precursors were studied. It was found that the good-quality epilayers were grown in the narrow range of the growth conditions. The valence to conduction band transition energies of such good-quality epilayers determined by the PR spectra are close to those for the bulk crystals. Stoichiometric CuAlSe₂ epilayers exhibited a yellow-green PL peak at 2.27 eV, which is the shortest-wavelength PL ever reported for CuAlSe₂ single crystals.