Origin of electrons emitted into vacuum from InGaN light emitting diodes

Journal Article · Tue Aug 05 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4892473· OSTI ID:1384260

Iveland, Justin ^[1]; Piccardo, Marco ^[2]; Martinelli, Lucio ^[3]; Peretti, Jacques ^[3]; Choi, Joo Won ^[4]; Young, Nathan ^[1]; Nakamura, Shuji ^[1]; Speck, James S. ^[1]; Weisbuch, Claude ^[2]

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1. Univ. of California, Santa Barbara, CA (United States)
2. Univ. of California, Santa Barbara, CA (United States); Centre National de la Recherche Scientifique (CNRS), Palaiseau Cedex (France)
3. Centre National de la Recherche Scientifique (CNRS), Palaiseau Cedex (France)
4. Seoul Viosys Co., Ltd. (Korea)

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 light 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.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Center for Energy Efficient Materials (CEEM)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0001009
• OSTI ID: 1384260
• Journal Information: Applied Physics Letters, Vol. 105, Issue 5; Related Information: CEEM partners with the University of California, Santa Barbara (lead); Purdue University; Los Alamos National Laboratory; National Renewable Energy Laboratory; ISSN 0003-6951
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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