Evidence for defect-assisted tunneling and recombination at extremely low current in InGaN/GaN-based LEDs

This paper investigates the electroluminescence characteristics of InGaN-based LEDs at extremely low current levels (down to 500 pA), i.e. in and below the region where recombination dynamics are governed by Shockley–Read–Hall recombination. Two different regimes are identified in the current–voltage characteristics, a first one below 100 nA associated to emission at wavelength below midgap, and a second one below 100 μA with a dominant emission at the quantum well wavelength. The experimental findings are interpreted by considering that, at extremely low current, carriers can tunnel towards states deeper than midgap, thus undergoing radiative recombination through defects.