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We submitted devices to 80 A/cm2 constant current stress, monitoring optical power and voltage by I-V and L-I characterization at each step. All the structures showed an increase in reverse leakage and low forward bias current, possibly due to trap-assisted tunneling ascribed to an increase in trap concentration. Reverse current was found to increase with the square root of stress time, indicating the presence of a diffusion process. The intensity of both QWs decreased during stress time; remarkably, degradation rate of reference QW (495 nm) was found to be much stronger for device B, where the 495 nm QW is closer to the p-side. The defects responsible for degradation were characterized by Steady-State Photocapacitance measurements, indicating the presence of a ~2 eV level, whose signal changes during stress time. Shallower defects were detected by C-DLTS, that identified a level with 0.284 eV activation energy, possibly related to VN, whose concentration decreases during stress, due to defect annealing. |
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Quantum wells
Indium gallium nitride
Light emitting diodes
Gallium nitride
