Direct Evidence for Generation of Defect Centers during Forward-Bias Degradation of GaAs1−xPxElectroluminescent Diodes

Direct evidence is presented for the generation of nonradiative defect centers in GaAs1−xPx electroluminescent diodes during forward-bias degradation. The defect centers, which have been observed by thermally stimulated current measurements, have concentrations between 5×1014 and 6×1015 cm−3 and lie 0.2–0.4 eV from either band edge. A qualitative correlation is established between the concentration of the induced defect centers and the extent of the electroluminescence efficiency reduction. In contrast to irradiation-induced defects previously described, defects due to long-term operation cannot be removed by annealing. This difference in annealing behavior is discussed in terms of the nature of defects formed in each case.