Luminescence properties of thick InGaN quantum-wells

In this paper, we discuss the physics of recombination in thick InGaN quantum-well (QW) based structures. Thick InGaN QWs have been suggested as one concept to reduce the typical decrease of internal efficiency of InGaN based light emitters towards high current densities. We show that at typical operation current densities, recombination in such thick QWs mainly originates from excited QW-states, which exhibit good electron hole overlap and large spatial extent, enabling a reduction of carrier density. We identify these states by comparing current dependent electroluminescence spectra to band structure simulations. The reduction of carrier density is verified by measuring current dependent carrier lifetimes. We find that saturation of efficiency is reduced for increasedQWthickness. However, the same effect can also be achieved using an MQW structure optimized for real MQW emission. We conclude that regardless of the employed concept, a decrease in carrier density is central to improve the high current efficiency of InGaN based light emitters.