| Abstract [eng] |
LEDs based on InGaN already present high internal quantum efficiencies, exceeding 90%. Nevertheless, there is still room for improvement, especially in the green emission region or at high non-equilibrium carrier densities. However, finding the optimal conditions for the growth of InGaN LEDs is burdened by a large number of variables in device fabrication and characterization; a single parameter to guide the technological efforts toward perfecting the InGaN LED design would ease the process. The diffusion coefficient of carriers might become such a parameter due to the negative correlation between carrier diffusivity and the peak quantum efficiency, which is revealed in this work. This tendency is seen among a large number of diverse samples, therefore diffusivity is suggested as a universal quantum efficiency limiting parameter. Reduction of the carrier diffusion coefficient by adjusting the quantum well thickness and modifying the growth procedures looks promising for further improvements in InGaN-based LEDs. The drop of quantum efficiency at higher carrier densities, known as the efficiency droop, is addressed in this work as well, with results pointing to a simultaneous occurrence of different mechanisms – diffusivity-driven non-radiative recombination at the defects and Auger recombination. It is suggested that whichever prevails is determined by localization conditions and the quality of the material, with Auger recombination having the main role in samples with high efficiency. |
