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Suggestions on Efficiency Droop of GaN-based LEDs
摘要： InGaN/GaN-based light-emitting diodes (LEDs) are widely used in modern society and industry among different areas. However, InGaN/GaN LEDs suffer from an efficiency droop issue: The internal efficiency decreases during high current injection. The efficiency droop significantly affects the development of GaN-based LEDs devices in efficiency and light-output areas. Therefore, the improvement of the droop phenomenon has become a significant topic. This paper introduces several possible mechanisms of droop phenomenon based on different hypotheses including Auger Recombination, Carrier Delocalization and Electron Leakage. Furthermore, some proposals to mitigate efficiency droop, including semipolar LEDs, electron blocking layer(EBL), quaternary alloy and chip design will be discussed and analyzed. Also, it will provide some suggestions for the further optimization of droop phenomenon in each proposal.
关键词： electron blocking layer,semipolar LEDs,GaN-based LEDs,Auger Recombination,chip design,quaternary alloy,Carrier Delocalization,Electron Leakage,efficiency droop
更新于2025-09-23 15:21:01
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Increased radiative recombination of AlGaN-based deep ultraviolet laser diodes with convex quantum wells
摘要： An AlGaN-based deep ultraviolet laser diode with convex quantum wells structure is proposed. The advantage of using a convex quantum wells structure is that the radiation recombination is significantly improved. The improvement is attributed to the increase of the effective barrier height for electrons and the reduction of the effective barrier height for holes, which results in an increased hole injection efficiency and a decreased electron leakage into the p-type region. Particularly, comparisons with the convex quantum barriers structure and the reference structure show that the convex quantum wells structure has the best performance in all respects.
关键词： AlGaN,radiation recombination,convex quantum wells,electron leakage,deep ultraviolet laser diode,hole injection efficiency
更新于2025-09-23 15:19:57
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Role of electron leakage on efficiency droop in AlxGa(1a??x)N/GaN ultraviolet LEDs
摘要： Highly efficient AlxGa1?xN/GaN deep ultraviolet LEDs are widely used for water purification and medical diagnostics. However, these LEDs undergo efficiency reduction problem known as efficiency droop. Many causes of efficiency droop have been found; out of these one strong cause is electron leakage (EL). Electrons are leaked from the active region of the device before recombination. Electron leakage in AlxGa1?xN/GaN deep ultraviolet LEDs depends on temperature and carrier concentration. Here we investigate efficiency droop phenomenon of AlxGa1?xN/GaN deep ultraviolet LEDs under the effect of polarization charges on carrier concentrations. It is found that efficiency is decreased when polarization and applied current increases.
关键词： Electron leakage (EL),Efficiency droop,Current density,UV LED,IQE,AlGaN/GaN
更新于2025-09-23 15:19:57
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Highly Efficient Quantum Dot Light‐Emitting Diodes by Inserting Multiple Poly(methyl methacrylate) as Electron‐Blocking Layers
摘要： This work presents a new device architecture integrating multiple poly(methyl methacrylate) (PMMA) electron-blocking layers (EBL) in quantum dot light-emitting diodes (QD-LEDs). The device utilizes red-emitting CdSe/ZnS QD with a novel structure where multiple PMMA EBLs are sandwiched between a pair of QD layers. A systematic optimization of QD-LED structures has shown that a device including two PMMA and three QD layers performs the best, achieving a current efficiency of 17.8 cd A?1 and a luminance of 194 038 cd m?2. Numerical simulation of a simplified model of the proposed QD-LED structure verifies that the structure consisting of two PMMA and three QD layers provides significant improvement in electroluminescent intensity. The simulation provides further insight into the origin of the effect of the PMMA EBL by showing that the addition of PMMA EBL reduces the electron leakage from the active QD region and enhances electron confinement, leading to an increased electron concentration in the QD active layers and a higher radiative recombination rate. The experimental and theoretical studies presented in this work demonstrate that multiple layers of PMMA can act as efficient EBLs in the fabrication of QD-LEDs of improved performance.
关键词： simulation,device architecture,electron-blocking layer,electron leakage,poly(methyl methacrylate) (PMMA),quantum dot light-emitting diodes (QD-LED)
更新于2025-09-19 17:13:59
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Improving Output Power of InGaN Laser Diode Using Asymmetric In0.15Ga0.85N/In0.02Ga0.98N Multiple Quantum Wells
摘要： Herein, the optical ?eld distribution and electrical property improvements of the InGaN laser diode with an emission wavelength around 416 nm are theoretically investigated by adjusting the relative thickness of the ?rst or last barrier layer in the three In0.15Ga0.85N/In0.02Ga0.98N quantum wells, which is achieved with the simulation program Crosslight. It was found that the thickness of the ?rst or last InGaN barrier has strong e?ects on the threshold currents and output powers of the laser diodes. The optimal thickness of the ?rst quantum barrier layer (FQB) and last quantum barrier layer (LQB) were found to be 225 nm and 300 nm, respectively. The thickness of LQB layer predominantly a?ects the output power compared to that of the FQB layer, and the highest output power achieved 3.87 times that of the reference structure (symmetric quantum well), which is attributed to reduced optical absorption loss as well as the reduced vertical electron leakage current leaking from the quantum wells to the p-type region. Our result proves that an appropriate LQB layer thickness is advantageous for achieving low threshold current and high output power lasers.
关键词： asymmetric multiple quantum wells,optical absorption loss,InGaN laser diodes,barrier thickness,electron leakage current
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 2nd International Conference on Electronics Technology (ICET) - Chengdu, China (2019.5.10-2019.5.13)] 2019 IEEE 2nd International Conference on Electronics Technology (ICET) - Increased Radiative Recombination in Nitride Laser Diodes with Inverse Tapered Electron Blocking Layer
摘要： A deep ultraviolet laser structure was proposed, which can lase at 261 nm band. In this simulation, the width of this laser diode was set to 4 μm and the cavity length was set to 530 μm. The mirror reflective index and the background loss were set to 0.05 and 2400, respectively. All the characteristics of the deep-UV laser diode were simulated under room temperature. The tapered EBL (electron bl1ocking layer), the inverse tapered EBL and the reference EBL were applied to this laser. When the tapered EBL is replaced by the inverse tapered EBL, the effective potential height of the EBL increased from 532 meV to 610 meV. This improvement means higher electronic blocking ability. More electrons will be confined to the active layer. Compared with the reference EBL, the electron leakage of inverse reduced about 22.7%. The concentration of carriers in the active layer is simulated. The radiative concentration increased by 1.48% for the inverse tapered EBL. The promotion of the radiative concentration indicated higher laser’s output power. The inverse tapered EBL is a far-reaching structure for laser diodes.
关键词： electron leakage,radiative recombination,laser diodes,the inverse tapered EBL
更新于2025-09-11 14:15:04
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Exploring Electronic and Excitonic Processes Towards Efficient Deep Red CuInS2/ZnS Quantum-dot Light-emitting Diodes
摘要： The electroluminescence mechanisms in the Cd-free CuInS2/ZnS quantum-dot based light-emitting diodes (QLEDs) are systematically investigated through transient electroluminescence measurements. The results demonstrate that the characteristics of hole transporting layers (HTLs) determine the QLEDs to be activated by the direct charge-injection or the energy-transfer. Moreover, both the energy level alignment between HTL and quantum dot and the carrier mobility properties of the HTLs are critical factors to affect the device performance. By choosing suitable HTL, such as 4,4'-bis(9-carbazolyl)-2,2'-biphenyl, highly efficient deep red (emission peak at ~650 nm) CuInS2/ZnS QLEDs based on single HTL can be obtained with peak current efficiency and luminance of ~2.0 cd/A and nearby 3000 cd/m2, respectively.
关键词： energy transfer,charge injection,hole-transport layer,QLEDs,electron leakage,charge accumulation
更新于2025-09-11 14:15:04