Excitonic Photoluminescence from CuGaSe₂ Single Crystals and Epitaxial Layers: Temperature Dependence of the Band Gap Energy

Abstract

Excitonic line spectra from CuGaSe 2 single crystals and epitaxial layers are investigated as a function of temperature. Near band edge luminescence from free and bound excitons is observed at 10 K. The identification of both, free exciton ground and first excited state allows to determine the free exciton binding energy, which is found to be (13±2) meV. The bound exciton line is attributed to the recombination of an exciton bound to a neutral acceptor (A 0 , X). The widely discussed phenomenon of an anomalous temperature dependence of the band gap energies in different chalcopyrite-type I-III-VI 2 compounds is reconsidered for CuGaSe 2 on the basis of temperature dependent photoluminescence studies. No anomalous behaviour of the band gap energy as a function of temperature is found in CuGaSe 2 .