Detailed photoluminescence study of Cu2Ge(SSe)3 microcrystals

We present a detailed temperature and laser power dependent photoluminescence (PL) study of Cu2Ge(S0.4Se0.6)3 microcrystals. At T = 20 K, two relatively narrow PL peaks were detected at about 1.16 eV (peak No. 1) and 1.12 eV (peak No. 2) and a weak, broad PL band was detected at about 0.82 eV (peak No. 3). The temperature and laser power dependencies indicate that at T = 20 K, the properties of PL peak Nos. 1 and 2 can be explained by the distant donor–acceptor (DA) pair model where a donor defect has a depth of ED ≈ 20 meV and ED ≈ 60 meV for peak Nos. 1 and 2, respectively. The depth of acceptor defects was 57 and 76 meV for peak Nos. 1 and 2, respectively. At around T = 90 K, the DA pair recombination of peak No. 1 gradually starts to transform into the conduction band–acceptor recombination, but peak No. 2 shows a DA pair recombination even at room temperature. The estimated bandgap energy of this compound at room temperature was Eg = 1.225 eV.