Exciton spectra and energy band structure of CuGaSe2 single crystals

Photoreflectivity, wavelength modulation spectroscopy and photoluminescence measurements of CuGaSe2 are used to determine the exciton and band parameters as well as the energy band structure of CuGaSe2 at photon energies higher than the fundamental band gap. The spectral dependences of the real epsilon(1) and imaginary epsilon(2) components of the complex dielectric function epsilon( E) = epsilon(1)( E) + i epsilon(2)( E) are calculated using the Kramers-Kronig relations. As a result, the energy band structure of CuGaSe2 at photon energies higher than the fundamental band gap is derived from the analysis of the structures observed both in the epsilon(omega) and in the wavelength modulated reflectivity spectra.