RADIATIVE RECOMBINATION IN CUINSE2 THIN-FILMS

We perform a detailed analysis of the radiative recombination processe s in CuInSe2 thin films grown by multisource physical vapor deposition . The photoluminescence and photoluminescence excitation spectra are i nvestigated as a function of stoichiometry, temperature and excitation intensity. Using samples with a large composition gradient, we are ab le to obtain a coherent picture of the optical transitions in the film s. The broad-band photoluminescence spectrum typical for In-rich films breaks into a number of well-defined emission lines in Cu-rich CulnSe (2). At low temperatures, emission peaks due to free-exciton, bound-ex citon, and free-to-bound recombination are identified in Cu-rich films . The spectra of In-rich films tend to be dominated by donor-acceptor transitions. From the optical spectra, exciton ionization energies and the temperature dependence of the band gap are determined. The observ ed optical transitions are related to intrinsic defects. (C) 1997 Amer ican Institute of Physics.