Temperature variation of nonradiative carrier recombination processes in high-quality CuGaSe2 thin films grown by molecular beam epitaxy

The piezoelectric photoacoustic (PPA) measurements for Cu-rich CuGaSe2(CGS)/GaAs(001) epitaxial layer were carried out between liquid helium and room temperatures. The band gap energies of CGS (A, B, and C bands) were measured to be 1.73, 1.83, and 2.04 eV at liquid nitrogen temperature, respectively. The A band was clearly obtained from 5 to 300 K, and the temperature dependence of the peak energy was fitted with the modified Manoogian–Woolley equation. PPA signals for CGS/GaAs (001) epitaxial layers were obtained between liquid helium and room temperature.