An ODMR investigation of the (Cu-Li)_Iand (Cu-Li)_IIIcomplex defects in GaP

Abstract

Co-doping of GaP with Cu and Li with a two-step diffusion procedure gives rise to several neutral associates involving both Cu and Li, as revealed by bound-exciton spectra in luminescence at low temperature. ODMR studies of two such associates are reported, the (Cu-Li)I centre with the lowest bound exciton lines at 2.3062 eV (triplet) and 2.3072 eV (singlet), and the (Cu-L:i)III centre which has four electronic bound-exciton lines in luminescence the lowest being a triplet a 2.2419 eV. In both cases the ODMR spectra show clear triplet resonances associated with the respective lowest-energy bound-exciton states. For (Cu-Li)I an orthorhombic distortion of a basically trigonal axial centre is deduced from the angular dependence of ODMR data, supporting an identification of the defect as Lii-CuGa-Lii where one Liei is bond-centred and the other is slightly distorted away from a tetrahedral interstitial site. For (Cu-Li)III the symmetry of this defect is very close to trigonal, suggesting an identification as Li1-CuGa-Cui where the Cui essentially remains in a tetrahedral interstitial position.