Hole injection and efficiency droop improvement in InGaN/GaN light-emitting diodes by band-engineered electron blocking layer

Wang, C. H.; Ke, C. C.; Lee, C. Y.; Chang, Shih-sen; Chang, Wen-Hao; Li, J. C.; Li, Z. Y.; Yang, Hung‐Chih; Kuo, Hao‐Chung; Lu, Tien−Chang; Wang, S. C.

doi:10.1063/1.3531753

Cited by 190 publications

(81 citation statements)

References 13 publications

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“…Thus, the combination of the blue chip with the phosphor dominates most part of the solid-state lighting (SSL) market [5,6]. In the past decade, there have been many studies focused on enhancing the characteristic of the GaN-based blue chip including the internal quantum efficiency [7], efficiency droop [8] and light extraction [9,10]. Furthermore, the air voids/SiO 2 nanomasks and nanopillar substrates are employed to improve the crystalline quality of the GaN-based epilayer and increase the output efficiency [11,12].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

et al. 2014

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This study demonstrates the hybrid structure with high lumen efficiency and uniform angular-dependent correlated color temperature (CCT) for warm white LED. Compared to the conventional structures, the hybrid structure combines the advantage of the two different fabrication methods including dispense and pulse spray method together, which can produce the high quality lighting source. The experimental results indicate that the hybrid structure yielded higher lumen efficiency than conventional phosphor structure because of the gradual refractive index difference from the coating layer to the dispense layer. Moreover, the CCT deviations of the hybrid phosphor structure could be reduced to 65 K in range of −70 to 70 degrees. This is attributed to the uniform color mixing of the blue, yellow and red band in the hybrid phosphor structure. In addition, the chromaticity coordinate shift compared to the hybrid structure with the dispense structure are almost the same at a current regulation from 20 mA to 500 mA. We believe that the technology of the hybrid structure with high lumen efficiency and uniform angular-dependent CCT is suitable for in the general lighting application.

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Section: Introductionmentioning

confidence: 99%

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

et al. 2014

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“…10 The asymmetry of carrier transport due to lower concentration and mobility of holes than those of electrons, which causes leakage of electrons out of the active region at high driving currents, was suggested as one of the major causes of efficiency droop. 11,12 Enhancement of the hole concentration at cryogenic temperatures by the field-enhanced ionization of acceptors 13,14 and improvement of hole-injection efficiency by energy-band-engineered electron-blocking layers (EBLs) 15,16 have been demonstrated to reduce efficiency droop, indicating that alleviation of such asymmetry is crucial for overcoming efficiency droop. Consequently, understanding the effect of the hole injection into the active region on radiative recombination behavior can provide an important clue for tackling efficiency droop by implementing suitable countermeasures.…”

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confidence: 99%

Modulation of hole-injection in GaInN-light emitting triodes and its effect on carrier recombination behavior

et al. 2015

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The effects of the hole injection modulated by using a three-terminal GaInN-based light emitter, light-emitting triode (LET), on carrier recombination behavior and efficiency droop are investigated. It was found that the lateral electric field created by applying voltage bias between the two anodes effectively reduces efficiency droop as well as dynamic conductance of LETs. Detailed analyses of LETs under various operation conditions by APSYS simulations reveal that the asymmetry in carrier transport between electrons and holes is alleviated by promoted injection of hot holes over the potential barrier, increasing the hole concentration as well as the radiative recombination rate in the multiple quantum well active region.

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“…Hole transportation is claimed to be one of the most important factors for causing the efficiency droop, such as nonuniform hole distribution in the multiple quantum wells (MQWs) and the low hole injection efficiency. [1][2][3] Consequently, tremendous efforts have been devoted to address these issues to improve the LED performance. As a result, structures such as engineered AlGaN electron-blocking layer (EBL), [3][4][5] p-type InGaN hole reservoir layer, 6 hole modulator by p-type doped last quantum barrier (QB), 7 AlGaN polarization doping, [8][9][10] and p-doped QBs, 11,12 etc., have been reported to enhance hole injection and reduce the efficiency droop.…”

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confidence: 99%

Investigation of p-type depletion doping for InGaN/GaN-based light-emitting diodes

Zhang

Tan

et al. 2017

Applied Physics Letters

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Due to the limitation of the hole injection, p-type doping is essential to improve the performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs). In this work, we propose and show a depletion-region Mg-doping method. Here we systematically analyze the effectiveness of different Mg-doping profiles ranging from the electron blocking layer to the active region. Numerical computations show that the Mg-doping decreases the valence band barrier for holes and thus enhances the hole transportation. The proposed depletion-region Mg-doping approach also increases the barrier height for electrons, which leads to a reduced electron overflow, while increasing the hole concentration in the p-GaN layer. Experimentally measured external quantum efficiency indicates that Mg-doping position is vitally important. The doping in or adjacent to the quantum well degrades the LED performance due to Mg diffusion, increasing the corresponding nonradiative recombination, which is well supported by the measured carrier lifetimes. The experimental results are well numerically reproduced by modifying the nonradiative recombination lifetimes, which further validate the effectiveness of our approach.

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Hole injection and efficiency droop improvement in InGaN/GaN light-emitting diodes by band-engineered electron blocking layer

Cited by 190 publications

References 13 publications

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

Enhancement of luminous efficiency by hybrid structure for warm white light-emitting diodes

Modulation of hole-injection in GaInN-light emitting triodes and its effect on carrier recombination behavior

Investigation of p-type depletion doping for InGaN/GaN-based light-emitting diodes

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