The phenomenon of light coalescence in Si light emitter during avalanche breakdown is investigated. DC stressing results in light coalescence for low values of current (<25 mA) with total light emission coming out of the junction remaining constant. However, DC stressing with large current values (>40 mA) do not show light coalescence. The light coalescence phenomenon can be reversed when emitters are subjected to higher levels of currents. The purpose of this paper is to explain the difference in light coalescence behavior for large and small values of DC excitations and the reversibility of the phenomenon using hydrogen migration model. (C) 2002 Elsevier Science Ltd. All rights reserved.