Magneto-photoluminescence study of radiative recombination in CuInSe 2 single crystals

Abstract

Radiative recombination processes in CuInSe 2 (CIS) single crystals grown by vertical Bridgman technique were studied using photoluminescence, photoluminescence excitation and magneto-PL. The PL and PLE spectra were measured as functions of temperature (varying from 4.2 to 300 K), excitation intensity, magnetic field (up to 10 T) and the elemental composition. The PL spectra taken at 4.2 K exhibited a complicated structure with a number of sharp peaks in the near-band-edge region associated with free ( E A =1.0416 eV, E B =1.0447 eV ) and bound excitons ( E M1 =1.0386 eV, E M2 =1.0353 eV, E M3 =1.0341 eV, E M4 =1.0324 eV and E M5 =1.0278 eV ) and free-to-bound recombination bands. The binding energies of the bound-excitons were derived. The nature of the defects associated with these excitons and the other observed bands is discussed. A non-linear blue shift toward higher energies was observed in magnetic field for all PL peaks. This shift is in agreement with the exciton energy calculated as a function of field. Field-induced splitting (4.5 meV at 10 T) of a deep band (0.972 eV) band was observed.