Efficient yellow luminescence from vapour grown gallium phosphide with high nitrogen content

Room temperature luminescence has been examined in nitrogen doped gallium phosphide grown by vapour epitaxy using the hydride system. Cathodoluminescence studies showed that as the nitrogen concentration was increased from 10 18 to 1.5*5*10 19 nitrogen atoms cm -3 the green A line (2.225 eV) was joined by the A-0 line (2.175 eV). At higher concentrations (5*10 19 atoms cm -3 ) the NN 1 line (2.10 eV) became dominant with the NN 1 -0 line (2.05 eV) becoming important at 1*10 20 nitrogen atoms cm -3 . The electroluminescence from p-n junction LED's made by zinc diffusion showed similar variations in spectral output. Diode efficiencies up to 0.1 per cent have been observed for diodes with emission peaking at 2.10 eV. Luminescence decay times of 40+or-4 ns have been observed in these diodes although these times were probably controlled by nonradiative transitions.