Changes in electrical characteristics associated with degradation of InGaNblue light-emitting diodes

Because of the high concentration of threading dislocations, the reverse cu rrent-voltage (I-V) characteristics for either homo- or heterojunctions mad e on GaN-based materials grown on sapphire often show a strong electric fie ld dependence (called a soft breakdown characteristic), which can be descri bed by a power law I = V-n, with n between 4 to 5. We find a significant in crease of reverse currents associated with the early degradation of emissio n in InGaN blue single-quantum-well light-emitting diodes (LEDs) subjected to aging tests (injected current of 70 mA over a total time of about 300 h) . The formation of dislocations might be due to the relaxation of strain in the thin InGaN active layer during the aging tests.