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

Chu, Chunshuang; Tian, Kangkai; Che, Jiamang; Shao, Hua; Kou, Jianquan; Zhang, Yonghui; Zhang, Zihui; Kuo, Hao‐Chung

doi:10.1109/jphot.2020.2997343

Cited by 18 publications

(7 citation statements)

References 32 publications

(44 reference statements)

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“…It can be seen that the overall electron leakage of Sample B is suppressed due to its higher ΔΦ e than Sample A, yet Sample C exhibits a further alleviated electron leakage because of its significantly higher ΔΦ e than Sample B and the electron depletion due to the absence of positive sheet charges at the LQB/Al 0.57∼0.75 Ga 0.43∼0.25 N interface. The significantly suppressed electron leakage can contribute to the obviously mitigated efficiency droop for the proposed DUV LEDs [16], [38], [39], as shown in Fig. 2(b).…”

Section: Resultsmentioning

confidence: 93%

“…In most cases, the external quantum efficiency (EQE) of AlGaN-based DUV LEDs is less than 10% and the efficiency droop phenomenon is quite severe [14], [15]. It has been reported that electron leakage and the insufficient hole injection are two crucial factors hindering the improvement of the optical and electrical properties of DUV LEDs [1], [16]. In order to suppress the electron leakage, a p-type electron blocking layer (p-EBL) is commonly grown between the last quantum barrier (LQB) and the hole supplier layer [1], [17].…”

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confidence: 99%

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Enhanced Carrier Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Polarization Engineering at the LQB/p-EBL Interface

Liu

2022

IEEE Photonics J.

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The external quantum efficiency (EQE) of AlGaNbased deep ultraviolet light-emitting diodes (DUV LEDs) is still far from satisfactory due to the main issues of electron leakage and insufficient hole injection. The positive sheet charges generated by polarization at the interface between the last quantum barrier (LQB) and the p-type electron blocking layer (p-EBL) can induce electron accumulation and hole depletion in the vicinity of this interface, leading to electron leakage and hindering the hole injection. In this paper, we propose an Al-composition-increasing AlGaN layer (ACI-AlGaN) inserted between the LQB and p-EBL to enhance the carrier injection ability of DUV LEDs via modulating the sheet charges generated by polarization at the LQB/EBL interface and the underlying mechanism was analyzed by numerical calculation. The inserted structure can eliminate the positive sheet charges at the p-side interface of LQB and induce hole accumulation in the vicinity of the n-side interface of p-EBL, which can subsequently reduce electron leakage and favor hole injection respectively. The proposed DUV LED structure with an ACI-AlGaN layer exhibited enhanced EQE by 45.7% and its forward voltage maintained undegraded. This design scheme can provide an alternative way to promote the performance of DUV LEDs with a variety of applications.

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Section: Resultsmentioning

confidence: 93%

mentioning

confidence: 99%

Enhanced Carrier Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Polarization Engineering at the LQB/p-EBL Interface

Liu

2022

IEEE Photonics J.

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“…The band-offset ratios for the InGaN/GaN and GaN/AlGaN heterojunctions are set to 0.70/0.30 and 0.50/ 0.50, respectively, which defines the ratio of the conduction band offset and the valence band offset [19,20] . The polarization level of 40% is assumed in our model for the GaN/AlGaN heterojunction [21,22] . The average optical loss for the p-GaN layer, the p-EBL, the MQWs, and the n-GaN layer in our modes is set to be 1000 m −1 .…”

Section: Device Structurementioning

confidence: 99%

Impact of p-AlGaN/GaN hole injection layer on GaN-based vertical cavity surface emitting laser diodes [Invited]

et al. 2022

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The hole injection capability is essentially important for GaN-based vertical cavity surface emitting lasers (VCSELs) to enhance the laser power. In this work, we propose GaN-based VCSELs with the p-AlGaN/p-GaN structure as the p-type hole supplier to facilitate the hole injection. The p-AlGaN/p-GaN heterojunction is able to store the electric field and thus can moderately adjust the drift velocity and the kinetic energy for holes, which can improve the thermionic emission process for holes to travel across the p-type electron blocking layer (p-EBL). Besides, the valence band barrier height in the p-EBL can be reduced as a result of usage of the p-AlGaN layer. Therefore, the better stimulated radiative recombination rate and the increased laser power are obtained, thus enhancing the 3 dB frequency bandwidth. Moreover, we also investigate the impact of the p-AlGaN/p-GaN structure with various AlN compositions in the p-AlGaN layer on the hole injection capability, the laser power, and the 3 dB frequency bandwidth.

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“…[15][16][17][18] In addition, the performance of AlGaN-LED devices would suffer due to the high polarization effect brought on by the strain between AlGaN layers. [19] Over the past ten years, numerous research teams have worked to find solutions to these difficulties in an effort to enhance the performance of DUV LEDs. An Al-rich p-AlGaN EBL can generally be inserted between the p-AlGaN and the last DOI: 10.1002/pssa.202200674…”

Section: Introductionmentioning

confidence: 99%

Efficient Carrier Confinement in AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with a Composition‐Graded Electron‐Blocking Layer

Cheng

Ren

et al. 2022

Physica Status Solidi (a)

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The serious electron leakage and poor transport of hole injection layers in deep‐ultraviolet (DUV) light‐emitting diodes (LEDs) lead to an imbalance between the hole and electron currents, which reduces the device's performance. Herein, a new DUV LED structure is designed. The aluminum composition of the p‐type electron‐blocking layer (p‐EBL) gradually decreases from 0.95 to 0.75 along the growth direction, replacing the traditional bulk p‐EBL. When the injection current is 100 mA, the optical power of this structure is about 32% higher than that of the traditional structure. In addition, when the p‐EBL adopts the opposite gradient (the Al composition gradually increases from 0.75 to 0.95), the device performance suddenly drops dramatically. The related devices are simulated by Silvaco TCAD software. The results show that the performance outputs of the two opposite aluminum gradient growth modes are completely opposite. The proposed p‐EBL with a gradual step‐down Al composition along the growth direction helps to improve the efficiency of hole injection into multiple quantum wells (MQWs) and reduce the level of electron leakage. This work provides an effective solution for increasing the light output power of high‐performance DUV LEDs.

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

Cited by 18 publications

References 32 publications

Enhanced Carrier Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Polarization Engineering at the LQB/p-EBL Interface

Enhanced Carrier Injection in AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Polarization Engineering at the LQB/p-EBL Interface

Impact of p-AlGaN/GaN hole injection layer on GaN-based vertical cavity surface emitting laser diodes [Invited]

Efficient Carrier Confinement in AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with a Composition‐Graded Electron‐Blocking Layer

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