Fig. 1. Electrical characterization during the stress, in semi-logarithmic scale, carried out before and during the stress experiment at 250 mA. All measurements were taken at 25°C.

Fig. 2. (a) Normalized current at the voltage of 3 V, and (b) normalized series resistance (Rs) at the temperatures of 25°C and 75°C during the stress.

Fig. 3. Ideality factor at the temperature of 25°C during the stress.

Fig. 4. (a) Optical power (OP) during the stress at the temperature of 25°C. (b) Normalized optical power at three different current levels: 10 μA, 1 mA, and 100 mA.

Fig. 5. Simplified representation of the increase in the injection barrier due to the presence of a distributed negative charge near/within the active region.

Fig. 6. Schematic representation of the reactions.

Fig. 7. Optical degradation measured at 25°C and 75°C during stress at 250 mA. Solid lines represent the solution of the system of ODEs reported above, showing a good agreement with the experimental data.

Fig. 8. Fitting of the optical power data at low current level with the function proposed in Ref. [24].

Fig. 9. Power spectral density during the aging at the current of 1 mA and at the temperature of 25°C.

Fig. 10. (a) SSPC measurement during the aging, and (b) correlation between the second defect from SSPC and the optical power at low current levels.