Abstract
Excitation power and temperature dependences of the steady-state photoluminescence (PL) spectra are studied in polycrystalline Cu2CdGeSe4 (CCGSe) containing a mixture of orthorhombic and tetragonal phases. The low-temperature excitation power dependences of the PL peak shape with a peak position at about 1.17 eV indicate a state filling effect. Reflectivity measurements revealed band gap energies 1.257 eV and 1.223 eV at 10 K and 300 K, respectively. The temperature dependences of the peak energy and linewidth showed a ‘S-shaped’ and ‘V-shaped’ behavior, respectively, and are well explained by the localized carriers model where band gap fluctuations play a crucial role. The asymmetric PL band shape analysis indicates the presence of hot carriers having a temperature about 75 K higher than the lattice temperature. It is shown that the low-temperature PL emission is due to recombination of localized electrons with holes captured by the deep acceptor defect CuCd with a depth EA = 80 meV.
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