Current-voltage characteristics of InGaN/GaN blue light-emitting diodes investigated by photovoltaic parameters

We investigate the current-voltage (I-V) characteristics of InGaN/GaN multiple-quantum-well blue light-emitting diodes (LEDs) to analyze the additional voltage drop outside the active region. We theoretically examine and measure the short-circuit current versus the open-circuit voltage (ISC-VOC) obtained by photoexcitation and compare them with the I-V obtained by electrical injection. The ISC-VOC curve shows the ideal I-V characteristics that do not contain the deviation from the exponential behavior. In the ideality factor obtained by differentiating the ISC-VOC curve, the increase of ideality factor due to the series resistance is not observed. The slope of the additional voltage drop ΔV versus current curve shows a nonlinear behavior, indicating that a simple ohmic voltage drop is not sufficient to explain ΔV. From these observations, it is concluded that the carrier recombination in the active region plays a non-negligible role in I-V characteristics of LEDs deviating from the ideal behavior.