Exciton spectra and energy band structure of CuGaSe2 single crystals

Abstract

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 ε1 and imaginary ε2 components of the complex dielectric function ε(E) = ε1 (E) + iε2(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 ε (ω) and in the wavelength modulated reflectivity spectra.