Electronic structure of the 2.087-eV bound exciton related to the ${\mathrm{Li}}_{\mathrm{i}}$-${\mathrm{Li}}_{\mathrm{Ga}}$-${\mathrm{O}}_{\mathrm{P}}$ complex defect in GaP

A detailed spectroscopic study of the 2.087-eV bound exciton (BE) in GaP, related to the ${\mathrm{Li}}_{\mathrm{i}}$-${\mathrm{Li}}_{\mathrm{Ga}}$-${\mathrm{O}}_{\mathrm{P}}$ neutral ‘‘isoelectronic’’ complex defect, is presented. Zeeman data for the BE lines have been analyzed with a complete Zeeman Hamiltonian, giving accurate values for the electron-hole exchange-splitting parameter a=0.77±0.02 meV and the crystal-field-splitting parameter D=1.66±0.02 meV. The isotropic g values for electron and hole are evaluated as $g_e$=1.76±0.05 and K=1.1±0.05. The relative oscillator strengths for the BE substates have been computed from the Hamiltonian and the assumed wave functions, in good agreement with experimental photoluminescence excitation data, if the experimental broadening of the higher-energy BE components is accounted for. The decay times for the different BE substates have also been measured at zero field at temperatures up to 50 K and compared with expected values from the oscillator strengths.