Understanding efficiency droop effect in InGaN/GaN multiple-quantum-well blue light-emitting diodes with different degree of carrier localization

Wang, Jiaxing; Wang, Lai; Zhao, Wei; Hao, Zhibiao; Luo, Yi

doi:10.1063/1.3520139

Cited by 107 publications

(72 citation statements)

References 21 publications

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“…It is difficult to quantify the increase in radiative lifetimes produced by the built-in electric fields because, as will be discussed in detail later, it is impossible to assign a single time constant to the radiative recombination process. Nevertheless, at low temperatures, energy dependent radiative decay times for InGaN/GaN QWs are quoted [15][16][17][18] to be $10 s of nanoseconds compared with exciton decay times in GaAs/AlGaAs QWs $100 s of picoseconds. 19 It is widely accepted 18,[20][21][22][23][24] that the carrier localisation can, to a large extent, overcome non-radiative recombination associated with defects.…”

Section: à2mentioning

confidence: 99%

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

Dawson

Schulz²,

Oliver

et al. 2016

Journal of Applied Physics

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In this paper, we compare and contrast the experimental data and the theoretical predictions of the low temperature optical properties of polar and nonpolar InGaN/GaN quantum well structures. In both types of structure, the optical properties at low temperatures are governed by the effects of carrier localisation. In polar structures, the effect of the in-built electric field leads to electrons being mainly localised at well width fluctuations, whereas holes are localised at regions within the quantum wells, where the random In distribution leads to local minima in potential energy. This leads to a system of independently localised electrons and holes. In nonpolar quantum wells, the nature of the hole localisation is essentially the same as the polar case but the electrons are now coulombically bound to the holes forming localised excitons. These localisation mechanisms are compatible with the large photoluminescence linewidths of the polar and nonpolar quantum wells as well as the different time scales and form of the radiative recombination decay curves.

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Section: à2mentioning

confidence: 99%

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

Dawson

Schulz²,

Oliver

et al. 2016

Journal of Applied Physics

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show abstract

“…However, the gradual decrease in internal quantum efficiency (IQE) with increasing input current, called efficiency droop, is a major obstacle in the widespread adoption of LEDs for general illumination. Many physical mechanisms including Auger recombination, 1,2 delocalization of carriers from In-rich low-defectdensity regions, 3,4 and electron leakage 5,6 have been proposed as the possible reasons for efficiency droop. Recently, Meyaard et al reported that the asymmetry in carrier transport, caused by much lower concentration and mobility of holes, compared with electrons, is the dominant mechanism causing for efficiency droop.…”

mentioning

confidence: 99%

Enhanced overall efficiency of GaInN-based light-emitting diodes with reduced efficiency droop by Al-composition-graded AlGaN/GaN superlattice electron blocking layer

Park

Kim

Hwang

et al. 2013

Applied Physics Letters

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AlxGa1−xN/GaN superlattice electron blocking layers (EBLs) with gradually decreasing Al composition toward the p-type GaN layer are introduced to GaInN-based high-power light-emitting diodes (LEDs). GaInN/GaN multiple quantum well LEDs with 5- and 9-period Al-composition-graded AlxGa1−xN/GaN EBL show comparable operating voltage, higher efficiency as well as less efficiency droop than LEDs having conventional bulk AlGaN EBL, which is attributed to the superlattice doping effect, enhanced hole injection into the active region, and reduced potential drop in the EBL by grading Al compositions. Simulation results reveal a reduction in electron leakage for the superlattice EBL, in agreement with experimental results.

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“…An understanding of the physical origin of the efficiency droop is critical for future progress in LEDs, particularly when operated at high current densities. Various mechanisms to explain the efficiency droop have been proposed, including delocalization of carriers [1,2], Auger recombination [3,4], and electron leakage [5,6]. Auger recombination (i.e., an electron drops non-radiatively from the conduction band to the valence band while transferring its energy to another electron or hole) has been regarded as a major cause of efficiency droop.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Imbalanced Carrier Transport on the Efficiency Droop in GaInN-Based Blue and Green Light-Emitting Diodes

et al. 2017

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Abstract:The effect of strongly-imbalanced carrier concentration and mobility on efficiency droop is studied by comparing the onset voltage of high injection, the onset current density of the droop, and the magnitude of the droop, as well as their temperature dependence, of GaInN-based blue and green light-emitting diodes (LEDs). An n-to-p asymmetry factor is defined as σ n /σ p , and was found to be 17.1 for blue LEDs and 50.1 for green LEDs. Green LEDs, when compared to blue LEDs, were shown to enter the high-injection regime at a lower voltage, which is attributed to their less favorable p-type transport characteristics. Green LEDs, with lower hole concentration and mobility, have a lower onset current density of the efficiency droop and a higher magnitude of the efficiency droop when compared to blue LEDs. The experimental results are in quantitative agreement with the imbalanced carrier transport causing the efficiency droop, thus providing guidance for alleviating the phenomenon of efficiency droop.

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Understanding efficiency droop effect in InGaN/GaN multiple-quantum-well blue light-emitting diodes with different degree of carrier localization

Cited by 107 publications

References 21 publications

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

The nature of carrier localisation in polar and nonpolar InGaN/GaN quantum wells

Enhanced overall efficiency of GaInN-based light-emitting diodes with reduced efficiency droop by Al-composition-graded AlGaN/GaN superlattice electron blocking layer

The Effect of Imbalanced Carrier Transport on the Efficiency Droop in GaInN-Based Blue and Green Light-Emitting Diodes

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