Interplay of point defects, extended defects, and carrier localization in the efficiency droop of InGaN quantum wells light-emitting diodes investigated using spatially resolved electroluminescence and photoluminescence
- Electrical and Computer Engineering Department and Energy Production and Infrastructure Center, University of North Carolina at Charlotte, Charlotte, North Carolina 28223 (United States)
- R and D Center for Semiconductor Lighting, Chinese Academy of Sciences, Beijing 100083 (China)
- Department of Electronic Science and Fujian Engineering Research Center for Solid-State Lighting, Xiamen University, Xiamen, Fujian 361005 (China)
We perform both spatially resolved electroluminescence (SREL) as a function of injection current and spatially resolved photoluminescence (SRPL) as a function of excitation power on InGaN quantum well blue light-emitting diodes to investigate the underlying physics for the phenomenon of the external quantum efficiency (EQE) droop. SREL allows us to study two most commonly observed but distinctly different droop behaviors on a single device, minimizing the ambiguity trying to compare independently fabricated devices. Two representative devices are studied: one with macroscopic scale material non-uniformity, the other being macroscopically uniform, but both with microscopic scale fluctuations. We suggest that the EQE–current curve reflects the interplay of three effects: nonradiative recombination through point defects, carrier localization due to either In composition or well width fluctuation, and nonradiative recombination of the extended defects, which is common to various optoelectronic devices. By comparing SREL and SRPL, two very different excitation/detection modes, we show that individual singular sites exhibiting either particularly strong or weak emission in SRPL do not usually play any significant and direct role in the EQE droop. We introduce a two-level model that can capture the basic physical processes that dictate the EQE–current dependence and describe the whole operating range of the device from 0.01 to 100 A/cm{sup 2}.
- OSTI ID:
- 22271251
- Journal Information:
- Journal of Applied Physics, Vol. 115, Issue 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
77 NANOSCIENCE AND NANOTECHNOLOGY
CAPTURE
CHARGE CARRIERS
COMPARATIVE EVALUATIONS
ELECTRIC CURRENTS
ELECTROLUMINESCENCE
EXCITATION
FLUCTUATIONS
GALLIUM NITRIDES
INDIUM COMPOUNDS
LIGHT EMITTING DIODES
PHOTOLUMINESCENCE
POINT DEFECTS
QUANTUM EFFICIENCY
QUANTUM WELLS
RECOMBINATION