Photoluminescence from transmuted impurities in neutron-transmutation-doped semi-insulating GaP

The transmuted impurities Ge and S in neutron-transmutation-doped (NTD) semi-insulating GaP were studied by a photoluminescence method. A broad emission was observed at 1.65 eV accompanied by a hump at ∼1.87 eV in samples annealed above 640°C. These emissions are attributed to GeGa–GeP complex and S donor–Ge acceptor pair recombination, respectively, indicating the presence of the transmuted impurities. The formation of the complex defect was examined using a configuration coordinate model. The presence of the complex defects restricted the electrical activation of the transmuted impurities in NTD-GaP, forming a localized state.