Efficiency droop in AlGaInP and GaInN light-emitting diodes

At room temperature, AlGaInP pn-junction light-emitting diodes (LEDs) emitting at 630 nm do not exhibit an efficiency droop. However, upon cooling the AlGaInP LEDs to cryogenic temperatures, they show a pronounced efficiency droop. We attribute the efficiency droop in AlGaInP LEDs to electron-drift-induced reduction in injection efficiency (i.e., carrier leakage out of the active region) mediated by the asymmetry of the pn junction, specifically the disparity between electron and hole concentrations and mobilities, with the concentration disparity exacerbated at low temperatures. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694044]The authors from Hanyang University acknowledge support from the Technology Innovation Program (Industrial Strategic Technology Development Program, 10032099, Development of commercialized technologies for performance and failure analyses of chip- or wafer-level light-emitting diodes) funded by the Ministry of Knowledge Economy (MKE, Korea). The authors from Rensselaer Polytechnic Institute gratefully acknowledge support from Samsung LED Co., Sandia National Laboratories (SNL), Department of Energy, Korean Ministry of Knowledge Economy and Korea Institute for Advancement of Technology through the International Collaborative R&D Program, National Science Foundation, Magnolia Optical Technologies, Inc., and Raydex Technology, Inc. D.S.M., G.B.L., J.C., and E.F.S. were supported by Sandia's Solid-State Lighting Sciences Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences