Excited states of the A free exciton in CuInS2

High quality CuInS2 single crystals, grown by the traveling heater method in an indium solvent, were studied using reflectance and photoluminescence at 4.2 K. The first, E-A(n=2)=1.5494 eV, and second, E-A(n=3)=1.5532 eV, excited states of the A free exciton have been observed in the photoluminescence spectra. Accurate values of the A exciton binding energy E-FE(A)=18.5 meV and Bohr radius a(B)(A)=3.8 nm, bandgap E-g=1.5540 eV at 4.2 K and static dielectric constant epsilon=10.2 have been derived assuming a hydrogenic model. (c) 2008 American Institute of Physics.