Luminescence and stimulated emission of polycrystalline Cu(In,Ga)Se$_{2}$ films deposited by magnetron-assisted sputtering

The stimulated emission of Cu(In,Ga)Se$_{2}$ alloy thin films formed by magnetron-assisted sputtering onto a sodium-fluoride layer deposited onto a molybdenum layer on a glass substrate is observed. The structural and optical parameters of the films are determined by scanning electron microscopy, local X-ray spectral microanalysis, X-ray structural analysis, and low-temperature luminescence ($T$ = 10 K) measurements in the range of excitation levels of 1.6–75 kW cm$^{-2}$ provided by nanosecond nitrogen-laser pulses. The stimulated emission threshold corresponds to $\sim$25 kW cm$^{-2}$. Comparative analysis of the emission of Cu(In,Ga)Se$_{2}$ thin films suggests that the introduction of sodium results in significant improvement of the structural quality, specifically, in a decrease in the density of energy states in the band tails and in a decrease in the concentration of nonradiative-recombination centers.