Current and light emission efficiency behaviors in GaN-based LEDS

Light emitting diodes (LEDs) with an InGaN/GaN multi-quantum wells structure have been fabricated. Their room temperature current-voltage characteristics and light emission efficiency behaviors under reverse-current stress and at different temperatures have been investigated. The forward current in the low-bias region is dominated by electron tunneling, while in the medium-bias region the heavy holes are the dominant tunneling entities. The reverse leakage current can be well explained with the defect-assisted tunneling model. The reverse-current stress induced additional structure defects in the active layer not only increase reverse-bias leakage current as leakage paths, but also degrade the overall efficiency of the LEDs as non-radiative recombination centers. The emission efficiency of the GaN-based LEDs is a strong function of temperature especially at low currents. With increasing temperature, the non-radiative recombination rate is enhanced at the extended structure defect, pushing the peak-efficiency current density toward the high current direction.