Extended defects such as threading dislocations reduces the quantum efficiency of InGaN light-emitting diodes (LEDs). There are a number of point defects around the threading dislocation sites resulting in a deep level states within the band gap. Charge carriers can tunnel through those states inducing a leakage current in the device [2]. The tunneling mechanism in LED device is only qualitatively described in a major of works. An analytical model is still missing.
In this work, we measured the reverse leakage current- voltage dependences of an InGaN LED above room temperature in the range of 293-523K. The phonon- assisted tunneling model developed by P. Pipinys et al. [1] was used to analyze the experimental data. The applied model showed good agreement with the current-voltage measurements, especially at high bias voltages (4-10V). We extracted two independed parameters from the model: the height of potential barrier and the density of states. The threading dislocations are non-radiative centers in an LED device. Therefore, it is possible to evalu- ate the density of such defects by performing scanning electron microscope (SEM) cathodoluminescence measurements. We systematically analyzed the SEM images and found out the threading dislocation density. The number of disloca- tions extracted from SEM showed good agreement with density of states evaluated from leakage current measurements. This result confirms that number of extended defects inside the device induce a leakage current that can be qualitatively estimated using phonon-assisted tunneling model.
