Efficiency droop in light‐emitting diodes: Challenges and countermeasures
TLDR
In this article, the authors present a theoretical model for the carrier leakage caused by the asymmetry of the pn junction, specifically the disparity between electron and hole concentrations and mobilities.Abstract:
Efficiency droop, i.e. the loss of efficiency at high operating current, afflicts nitride-based light-emitting diodes (LEDs). The droop phenomenon is currently the subject of intense research, as it retards the advancement of solid-state lighting which is just starting to supplant fluorescent as well as incandescent lighting. Although the technical community does not yet have consented to a single cause of droop, this article provides a summary of the present state of droop research, reviews currently discussed droop mechanisms, and presents a recently developed theoretical model for the efficiency droop. In the theoretical model, carrier leakage out of the active region caused by the asymmetry of the pn junction, specifically the disparity between electron and hole concentrations and mobilities, is discussed in detail. The model is in agreement with the droop's key behaviors not only for GaInN LEDs but also for AlGaInP LEDs.read more
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References
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Efficiency retention at high current injection levels in m-plane InGaN light emitting diodes
Xing Li,Xianfeng Ni,J. Lee,Mingzhong Wu,Ümit Özgür,Hadis Morkoç,Tanja Paskova,G. Mulholland,Keith R. Evans +8 more
TL;DR: In this article, the internal quantum efficiency and the relative external quantum efficiency of m-plane InGaN light emitting diodes (LEDs) were investigated for current densities up to 2500 A/cm2.
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Simulation of visible and ultra-violet group-III nitride light emitting diodes
TL;DR: Simulations of a number of single- and multiple-quantum well blue and ultraviolet light emitting diodes are presented and compared with available observations and applicability of the drift-diffusion model to analysis of III-nitride LEDs is proved.
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On resonant optical excitation and carrier escape in GaInN/GaN quantum wells
TL;DR: In this paper, it was shown that carrier escape from quantum wells does take place and shows strong dependence upon the duration of excitation and bias conditions, and the time scales required to reach steady-state conditions under pulsed optical excitation.
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Improvements of external quantum efficiency of InGaN-based blue light-emitting diodes at high current density using GaN substrates
TL;DR: In this article, the external quantum efficiencies (EQEQEs) of LEDs on GaN substrates, as well as those on sapphire substrates were shown to decrease with increasing forward current.
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Probing the electrostatic potential of charged dislocations in n-GaN and n-ZnO epilayers by transmission electron holography
TL;DR: In this paper, the electrostatic potential in the vicinity of charged dislocations was determined from the reconstructed phase of the electron wave, which also provided access to the charge density at the dislocation.