Changes in Electrical Characteristics Associated With Degradation of InGaN Blue Light-Emitting Diodes

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Because of the high concentration of threading dislocations, the reverse current-voltage (I-V) characteristics for either homo- or heterojunctions made on GaN-based materials grown on sapphire often show a strong electric field dependence (called a soft breakdown characteristic), which can be described by a power law I = V-n, with n between 4 to 5. We find a significant increase of reverse currents associated with the early degradation of emission 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.