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Title: Origin of electrons emitted into vacuum from InGaN light emitting diodes

The mechanism responsible for efficiency droop in InGaN light-emitting diodes (LEDs) has long been elusive due to indirect measurement techniques used for its identification. Auger recombination is unique among proposed efficiency droop mechanisms, in that it is the only mechanism capable of generating hot carriers. In a previous study [J. Iveland et al., Phys. Rev. Lett. 110, 177406 (2013)], we performed electron energy analysis of electrons emitted into vacuum from a forward biased InGaN LED that had been brought into negative electron affinity by cesiation. Three peaks were observed in the energy spectrum of vacuum emitted electrons. In this Letter, we unambiguously identify the origin of the peaks. The two higher energy peaks correspond to accumulation of electrons transported to the surface in the bulk Γ and side L conduction band valleys. The L-valley peak is a direct signature of a hot Auger electron population. The lower energy peak results from surface photoemission induced by the internal LED light emitted from the InGaN quantum wells. Two control experiments were performed. In the first, a simple GaN pn junction generated only a single Γ peak in electroemission. In the second, selective detection of the photoemission from an LED under modulated lightmore » excitation and DC electrical injection confirms that only the low energy peak is photogenerated and that LED light is incapable of generating Γ or L-valley peaks, the latter only occurring due to the Auger effect in the LED active region.« less
Authors:
; ;  [1] ; ;  [1] ;  [2] ; ;  [3] ;  [4] ;  [1] ;  [5]
  1. Materials Department, University of California, Santa Barbara, California 93106-5050 (United States)
  2. (France)
  3. Laboratoire de Physique de la Matière Condensée, CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex (France)
  4. Seoul Viosys Co., Ltd., 1-36 727, Won-Si Dong, Danwon-Gu, Ansan City, Kyunggi-do 425-851 (Korea, Republic of)
  5. (United States)
Publication Date:
OSTI Identifier:
22314487
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; EFFICIENCY; ELECTRONS; ENERGY SPECTRA; GALLIUM COMPOUNDS; INDIUM COMPOUNDS; LIGHT EMITTING DIODES; NITROGEN COMPOUNDS; PHOTOEMISSION; QUANTUM WELLS; SEMICONDUCTOR JUNCTIONS