Origin of the low-forward leakage current in InGaN-based LEDs

We investigate the electroluminescence of blue LEDs in low bias (500 pA – 9 μA) at different temperature (15°C – 75°C). From 500 pA to 100 nA, the OP increases with bias current up to 10nA, and is stronger at higher temperature, as expected by radiative recombination through deep levels. The stronger contribution is at λ > 800 nm, i.e. at energies lower than the QW and GaN barrier midgap (720 nm). Above 100 nA the OP increases with current, and is compatible with QW emission. Its intensity decreases at higher temperature, as expected for non-radiative recombination. The experimental findings indicate that radiative recombination through deep levels can significantly influence the low current characteristics of the devices, even when those states are not at midgap.