Both diffused and alloyed junctions were prepared from single crystals of GaP cut from ingots grown near the melting point, as well as from crystals grown at lower temperatures. The diodes were characterized by their current‐voltage relationship and their capacity at reverse bias. Anomalies in both the forward and the reverse currents, an excess capacity, and a hysteresis effect are attributed to the presence of deep centers in the depletion layer, particularly in the alloyed structures. A nearly compensated layer was found at the junction of the diffused diodes. The spectra, bias dependences, decay times, and efficiences of the electro‐luminescence emitted at these junctions at both forward and reverse bias were studied and correlated with the diode models. At reverse bias, radiative intraband relaxation was due to carriers excited during avalanche breakdown (diffused diodes), by internal field emission (alloyed diodes), and from carriers thermally generated within the depletion layer (all diodes). At forward bias, only the diffused junctions exhibited light emission and this was of two types: (1) a band‐to‐band recombination with phonon cooperation, whose recombination kinetics depended on whether or not the process occurred within the depletion layer, and (2) recombination through a deep level which may be associated perhaps with a vacancy.