Efficiency degradation and deep-level change in GaP red LED's

The efficiency degradation of GaP red light-emitting diodes was studied by junction techniques, namely photocapacitance (PHCAP), thermally stimulated capacitance, and thermally stimulated current. Diodes were sorted into two types; type A shewed large degradation and type B smaller degradation. Four minority carrier traps were found before degradation and at least two majority carrier traps after degradation. The appearance of new majority carrier traps correlates with the degradation of efficiency. These traps caused the anomalous PHCAP spectrum shift. The energy levels of the traps are 0.55 and 0.76 eV with the concentration of the order of 10
¹⁵
cm
^-3
. The density of isolated oxygen donors did not change.