Ultrathin inserted AlGaN/InAlN heterojunction for performance improvement in AlGaN-based deep ultraviolet light-emitting diodes

Li, Lei; Miyachi, Yuta; Miyoshi, Makoto; Egawa, Takashi

doi:10.7567/1882-0786/aaf62b

Cited by 27 publications

(16 citation statements)

References 27 publications

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“…The

\left(\text{E}\right)_{\text{k}}

of the holes increases with the electric field strength, which makes it easier for holes to through the triangular LQB. [ 41 ] However, adopting a triangular LQB will increase the electric field strength in the LQW, which is detrimental to the radiative recombination in the QWs.…”

Section: Resultsmentioning

confidence: 99%

Performance Improvement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Multigradient Electron Blocking Layer and Triangular Last Quantum Barrier

Cao

et al. 2023

Physica Status Solidi (a)

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The performance improvements of AlGaN‐based deep ultraviolet light‐emitting diodes (DUV‐LEDs) with multigradient electron blocking layer (EBL) and triangular last quantum barrier (LQB) are investigated. The results show that the maximum internal quantum efficiency (IQE) is improved by 44.9% and light output power (LOP) is improved by 58.1% at 200 A cm−2, exhibiting a tremendous improvement compared to the conventional structure. These improvements are mainly attributed to the fact that both multigradient EBL and triangular LQB can generate negative polarization charges in the graded composition layer, which leads to a significant increase in hole concentration compared to the conventional EBL and LQB structures. Meanwhile, the multigradient EBL can transform the conventional triangular barrier into an arc‐shaped barrier, increasing the electron potential barrier height and decreasing the hole potential barrier height. This unique design suppresses electron leakage and enhances hole injection, leading to a significant enhancement of the IQE and alleviation of the efficiency droop.

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“…The

\left(\text{E}\right)_{\text{k}}

Section: Resultsmentioning

confidence: 99%

Performance Improvement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Multigradient Electron Blocking Layer and Triangular Last Quantum Barrier

Cao

et al. 2023

Physica Status Solidi (a)

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“…It has been demonstrated that In0.18Al0.82N is nearly lattice-matched with GaN and could bring about a better performance when used as the EBL in visible LEDs [40]. Moreover, the InAlN alloys could be applied to UV LEDs with lower indium compositions and thus larger bandgap [41]. On the other hand, it is not straightforward to grow high quality InAlN because of phase separation and composition inhomogeneity [42], [43].…”

Section: (B) Besides > Replace This Line With Your Manuscript Id Number (Double-click Here To Edit) <mentioning

confidence: 99%

Polarization Modulation at Last Quantum Barrier for High Efficiency AlGaN-Based UV LED

Liu

Wang

et al. 2022

IEEE Photonics J.

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The performance of AlGaN-based light-emitting diodes (LEDs) emitting at UVA-UVC regions can be severely compromised due to the polarization difference (∆P) between the last quantum barrier (LQB) and the electron blocking layer (EBL). In this work, the different situations of the bandgap difference (∆Eg) and ∆P of InAlN/AlGaN and AlGaN/AlGaN heterojunctions fully strained on GaN and AlN substrates are discussed. It shows that the InAlN/AlGaN heterojunctions could produce positive or negative sheet charges at the heterointerface under ∆Eg >0, which could not be realized by the conventional AlGaN/AlGaN heterojunctions. To demonstrate and utilize the feature, the polarization-modulated InAlN LQBs with 0.14-0.16 indium compositions of 320 nm UVB LEDs are designed and investigated. It is observed that the InAlN LQBs could replace the conventional AlGaN LQB to improve electron confinement and hole injection by affecting effective barrier heights. By modulating the LQB/EBL polarization using InAlN, the proposed UV LED has a 32% enhancement in internal quantum efficiency and lower efficiency droop (from 16.9% to 0.7%) compared with the conventional one without modulation. The operation voltage at the same current also significantly decreases. The improvement of optical output power and wall plug efficiency at 60 mA in proposed structures are near 90% and 100%, respectively. This study provides a novel and highly effective methodology for development of high efficiency UV LEDs.

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“…The theory has been proved to be effective in both blue and DUV LEDs with graded p-type AlGaN layer [19]- [23]. In addition, some researchers found that by taking advantage of the tunneling process, the conventional thermionic emission process limited by the potential barrier can be bypassed and thus the hole injection efficiency can be boosted effectively [12], [24], [25]. Furthermore, we reported that the hole injection of blue LEDs can be boosted by introducing a series of shallow wells in the valence band with an InGaN/GaN superlattice layer [26].…”

Section: Introductionmentioning

confidence: 99%

Sheet Charge Engineering Towards an Efficient Hole Injection in 290 nm Deep Ultraviolet Light-Emitting Diodes

Liu

Zhou

et al. 2021

IEEE Photonics J.

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The hole injection efficiency is one of the bottlenecks that restricts the external quantum efficiency (EQE) and optical power of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). The polarization-induced positive sheet charges at the last quantum barrier (LQB)/electron blocking layer (EBL) interface reflect the holes back to the p-type layer and weaken the hole injection capability into the active region. In this work, we designed and incorporated a polarization-engineered AlxGa1-xN/AlyGa1-yN superlattice layer at the LQB/EBL interface. The positive sheet charges at the LQB/EBL interface can be inverted into negative charges with optimal Al compositions in the AlxGa1-xN/AlyGa1-yN superlattice layer. The electron confinement and hole injection efficiency can also be improved through increasing the effective barrier height for electrons and decreasing the effective barrier height for holes, resulting in an enhanced optical power by 29.4% and alleviated efficiency droop by 78.4% for the proposed device with an Al0.67Ga0.33N/Al0.7Ga0.3N superlattice insertion layer. The sheet charge engineering method by polarization provides an alternative approach to boost the hole injection efficiency towards an enhanced device performance for DUV LEDs.

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Ultrathin inserted AlGaN/InAlN heterojunction for performance improvement in AlGaN-based deep ultraviolet light-emitting diodes

Cited by 27 publications

References 27 publications

Performance Improvement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Multigradient Electron Blocking Layer and Triangular Last Quantum Barrier

Performance Improvement of AlGaN‐Based Deep‐Ultraviolet Light‐Emitting Diodes with Multigradient Electron Blocking Layer and Triangular Last Quantum Barrier

Polarization Modulation at Last Quantum Barrier for High Efficiency AlGaN-Based UV LED

Sheet Charge Engineering Towards an Efficient Hole Injection in 290 nm Deep Ultraviolet Light-Emitting Diodes

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