A gallium phosphide photovoltaic junction is reported. Using a n-p structure, a gallium phosphide junction is grown on a gallium phosphide substrate by molecular beam epitaxy. junction design is presented with measurements of the dark and light response. The light current was measured under an illumination of air mass (AM) 1.5. Without an anti-reflective coating, a V-oc of 1.53 V and a J(sc) of 0.959 mA/cm(2) is achieved at one-sun AM1.5 global. A simulation of the junction is presented with best-fit parameters. Strategies for efficiency improvements are discussed which yield a simulated V-oc of 1.93 V and an AM 1.5 efficiency of 14% at 20 suns. Justification of a 51.3% efficient, ideal, multi-junction device is also presented. (C) 2010 Elsevier B.V. All rights reserved.