Blue light emitting diode exceeding 100 % quantum efficiency

1 Introduction GaN-based light-emitting diodes (LEDs) deliver the desired high efficiency only at relatively low injection current density [1]. At the elevated current densities required in practical high-brightness applications , the efficiency is substantially reduced. This efficiency droop phenomenon has been intensely investigated for a number of years, but the physical mechanisms behind it are still disputed [2]. Among the proposed droop explanations are density-activated defect recombination (DADR) [3], enhanced Auger recombination [4], and electron leakage into the p-doped layers [5]. In all three droop models, the rising quantum well (QW) carrier density causes increasing carrier losses due to non-radiative re-combination or leakage. Thus, a possible solution lies in the reduction of the QW carrier density required for a given output power by increasing the number of QWs. But this approach is hampered by the non-uniform vertical carrier distribution commonly observed with thick InGaN