Sharp-line and broad-band emission in AgGaS2 crystals

Abstract

The low-temperature photoluminescence spectra of AgGaS2 are investigated in this work. At 4.2°K, the luminescence spectra are dominated by many sharp lines as well as broad emission bands. A series of emission lines was found to be superimposed on the broad band peaking at ∼ 5000 Å. The series of emission lines are attributed to phonon-assisted transitions involving an unidentified impurity or defect. Two basic phonons with energies of 5.4 and 7.2 meV are identified from the phonon structure. The 7.2-meV mode is also seen in the Raman spectrum. They are tentatively identified as the lattice modes.