Progress in External Quantum Efficiency for III‐Nitride Based Deep Ultraviolet Light‐Emitting Diodes

Chu, Chunshuang; Tian, Kangkai; Zhang, Yonghui; Bi, Wengang; Zhang, Zihui

doi:10.1002/pssa.201800815

Cited by 40 publications

(20 citation statements)

References 131 publications

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“…Although the record value of the external quantum efficiency (EQE) of UVC LEDs on c-sapphire can reach 20.3%, as has been demonstrated by Riken's group in 2017, [12] for other commercial and R&D UVC and UVB LEDs, the EQE does not exceed a few percent. [23,24] The same low EQE values are observed even for UV LEDs grown on expensive bulk AlN substrates and much nontrivial improvements are still necessary to achieve the 35% efficiency, which is typical for alternative UVC Hg lamps with a fixed wavelength of 254 nm.Extremely slow progress has been made in the development of AlGaN-based UV lasers, where only the single group from Nagoya University has recently demonstrated a laser diode (LD) generating sub-300 nm radiation with an emission wavelength λ ¼ 271.8 nm and a threshold current of 25 kA cm À2 . [25]…”

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confidence: 88%

Monolayer‐Thick GaN/AlN Multilayer Heterostructures for Deep‐Ultraviolet Optoelectronics

Jmerik

Торопов

Davydov

et al. 2021

Physica Rapid Research Ltrs

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Recent progress in the development of monolayer (ML)‐thick GaN/AlN multilayer heterostructures for deep‐ultraviolet (UV) optoelectronics is reviewed. Analysis of both plasma‐assisted molecular beam epitaxy and metal–organic vapor phase epitaxy shows that extreme interface sharpness and sub‐ML accuracy in setting the layer thickness are attractive features of the former, whereas the lowest density of threading dislocations and wide possibilities for the implementation of various 2D growth mechanisms are the advantages of the latter. The structural properties of ML GaN/AlN heterostructures are evaluated not only by standard X‐ray diffraction and scanning transmission electron microscopy, but also by Raman spectroscopy. Theoretical and experimental studies of the optical properties of ML‐thick GaN/AlN quantum wells (QWs) reveal that quenching of the quantum‐confined Stark effect, suppression of transverse electric transverse magnetic polarization switching, as well as the excitonic nature of UV‐radiative recombination in ultrathin (1–2 ML) QWs ensure in such structures a high internal quantum yield of 75% for UV radiation at 235 nm at room temperature. The possibilities of using ML‐GaN/AlN heterostructures to fabricate UVC emitters of spontaneous and stimulated emissions in a wide range of output powers with various pumping techniques are considered, and the most important problems are formulated.

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confidence: 88%

Monolayer‐Thick GaN/AlN Multilayer Heterostructures for Deep‐Ultraviolet Optoelectronics

Jmerik

Торопов

Davydov

et al. 2021

Physica Rapid Research Ltrs

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“…On the other hand, a reduced efficiency droop can be obtained if the Auger recombination decreases, which is realizable by making quantum wells in flat band condition [16]. The efficiency droop for EQE is also observed for AlGaN-based DUV LEDs, which can be higher than 10% [17], [18]. As reported, the efficiency droop decreases from 54% to 34% when an n-AlN/AlGaN EBL is utilized [19].…”

Section: Introductionmentioning

confidence: 66%

On the Impact of Electron Leakage on the Efficiency Droop for AlGaN Based Deep Ultraviolet Light Emitting Diodes

et al. 2020

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In this work, we have investigated the origin of efficiency droop for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). We find that the efficiency droop is likely to be caused by the electron leakage for DUV LEDs studied in this work. The electron leakage arises from the unbalanced electron and hole injection efficiencies. The correlation between the efficiency droop and the electron leakage can be numerically calculated by manipulating the conduction band barrier height of the p-AlGaN electron blocking layer (p-EBL) for the proposed DUV LEDs. For the purpose of demonstrating that the efficiency droop for DUV LEDs can be experimentally decreased by reducing the electron leakage, a p +-GaN/In 0.15 Ga 0.85 N/n +-GaN tunnel junction on DUV LED is grown by using metal organic chemical vapor deposition (MOCVD) technology. The tunnel junction helps to enhance the hole injection, thus decreasing the electron leakage and the efficiency droop. Moreover, the parasitic emission in the p-type hole injection layer is no longer observed thanks to the decreased electron leakage level.

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“…[3][4][5] Today, the best UVB LEDs exhibit an external quantum efficiency in the range of only a few percent. [6][7][8][9][10][11] Optimization of the semiconductor heterostructure is very important to improve the output power, the operating voltage, and the lifetime of UV LEDs. Therefore, we have previously discussed the influence of the nlayer heterostructure design, [12] the quantum well (QW), and quantum-barrier composition, [13] the QW width [14] as well as the electron blocking layer (EBL) design [15,16] on the emission characteristics and efficiency of triple quantum well (TQW) LEDs in the UVB spectral region.…”

Section: Introductionmentioning

confidence: 99%

“…[ 3–5 ] Today, the best UVB LEDs exhibit an external quantum efficiency in the range of only a few percent. [ 6–11 ]…”

Section: Introductionmentioning

confidence: 99%

Comparison of Ultraviolet B Light‐Emitting Diodes with Single or Triple Quantum Wells

Kolbe

Knauer

Ruschel

et al. 2021

Physica Status Solidi (a)

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Light‐emitting diodes (LEDs) with an emission wavelength of 310 nm containing either a single or a triple quantum well are compared regarding their efficiency and long‐term stability. In addition, the influence of the thickness of the lower quantum well barrier and the quantum well thickness in single quantum well (SQW) LEDs is investigated. Electroluminescence measurements show a 28% higher initial output power for the SQW LEDs compared with the triple quantum well (TQW) LEDs because of larger spatial overlap of the carriers in the SQW as revealed by electro‐optical simulations of the LED heterostructures. However, TQW LEDs show a higher output power than SQW LEDs after 1 h operation under harsh conditions. For SQW LEDs, it is found that for a thicker lower quantum well barrier (65 nm instead of 25 nm) the initial output power decreases by ≈15%. A thicker SQW (3 nm instead of 1.6 nm) reduces the initial output power by even 45% but increases the lifetime by a factor of 6 which is attributed to reduced Auger recombination from an enhanced spatial separation of electrons and holes in the quantum wells due to the quantum‐confined Stark effect.

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Progress in External Quantum Efficiency for III‐Nitride Based Deep Ultraviolet Light‐Emitting Diodes

Cited by 40 publications

References 131 publications

Monolayer‐Thick GaN/AlN Multilayer Heterostructures for Deep‐Ultraviolet Optoelectronics

Monolayer‐Thick GaN/AlN Multilayer Heterostructures for Deep‐Ultraviolet Optoelectronics

On the Impact of Electron Leakage on the Efficiency Droop for AlGaN Based Deep Ultraviolet Light Emitting Diodes

Comparison of Ultraviolet B Light‐Emitting Diodes with Single or Triple Quantum Wells

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