Subthreshold characteristics of GaN-based LEDs: trap-assisted tunneling and coupled defects

The presence of defects in GaN-based LEDs is frequently associated with the efficiency droop. It is therefore interesting to study the sub-threshold diode current, where nonradiative recombination effects appear more evident. In this work, we reproduce the high ideality factors observed in the I-V characteristics of GaN-based LEDs by means of a quantum corrected drift-diffusion model based on the solution of the Schroedinger equation. Our results indicate that, in highly defective structures, the anomalous characteristics cannot be entirely attributed to trap-assisted tunneling as previously assumed. We conclude that the unexpectedly large ideality factors observed in GaN-based LEDs can be explained by extending the conventional theory of SRH theory of isolated recombination centers to the case of coupled defects.