Impurity absorption and luminescence of CuGaSe2 crystals

A comparison of the experimental and calculated absorption spectra of CuGaSe₂ crystals revealed the existence of two acceptor levels with ionization energies of 66 and 167 meV in the samples under study. It was found that the luminescence spectra of CuGaSe₂ measured at 77 K exhibit four impurity-band transitions with impurity ionization energies of 66, 99, 136, and 190 meV. An analysis of the temperature dependence of the luminescence intensity in the temperature range 11–77 K revealed a band peaking at 1.671 eV due to the radiation of donor-acceptor pairs. The calculated sum of the ionization energies of the impurities responsible for the formation of donor-acceptor pairs and the temperature dependence of the relative intensities of impurity-band emission were used to determine the ionization energies of the corresponding donor and acceptor.