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

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Abstract
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 1018 to 1.5*5*1019 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*1019 atoms cm-3) the NN1 line (2.10 eV) became dominant with the NN1-0 line (2.05 eV) becoming important at 1*1020 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.