Photoluminescence and scanning-electron-microscope measurements of minority-carrier lifetime and luminescence efficiency have been made on Zn, N-doped and Te, N-doped GaP liquid-phase-epitaxy layers. Nitrogen concentrations are held constant at 1 × 1019 cm−3, while the majority-carrier concentrations were varied between 5 × 1016 and 5 × 1018 cm−3. It is shown that, for excitation levels equivalent to 10 A/cm2 diode diffusion current density, a maximum external luminescence efficiency (in air) of 0.3% is measured for ∼1018-cm−3 Zn, N-doped GaP, in contrast to a maximum efficiency of 0.06% for ∼1017-cm−3 Te, N-doped GaP. These results suggest that significantly higher electroluminescent efficiencies approaching 0.3% are available for diodes at 10 A/cm2, by increasing injection into ∼1018-cm−3 Zn, N-doped GaP.