We propose an optimal design for enhancing the external quantum efficiency of InGaN/GaN LEDs operating in the green spectral region, by mediating surface plasmons (SP), showing that there is plenty of potential for additional improvement in this area. Coupling the spontaneous emission from quantum wells into SP modes on metallic grating structures could enhance the internal quantum efficiency of conventional LEDs by more than twofold, and the relatively long propagating length of SPs in the green region could allow a narrow radiating angle and thus yield a threefold improvement in the extraction efficiency of radiation. Thus, our design enhances external quantum efficiency by about sixfold overall, offering a practically attainable method to realize highly efficient green SP-LEDs. (C) 2014 Elsevier B.V. All rights reserved.