Electroluminescence (EL) characteristics of avalanching diodes fabricated by Er and O co-implantation and subsequent annealing have been studied. Distribution of Er3+-related EL at 1.538 μm was found to be uniform over the device area at 300 K. Saturation of the Er-related EL intensity is achieved under the avalanche regime at current density one order of magnitude lower than that under the tunnel regime. An EL decay is less than 10 μs (being time response of our detector) after the diode turned off the avalanche regime.