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Polarization-engineered AlGaN last quantum barrier for efficient deep-ultraviolet light-emitting diodes
摘要： The AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) has been identified as a prospective mercury-free UV source. However, the observation of severe electron overflow and low hole injection efficiency in the conventional DUV LED deteriorates the device performance, attributing to the downward band bending as a result of the strong polarization-induced electric fields between the last quantum barrier (LQB) and the electron blocking layer (EBL). In this study, a composition-graded AlGaN layer with linearly increasing of Al composition from 0.5 to 0.65 is proposed to act as the LQB, replacing the conventional flat LQB to reduce the effective barrier height for hole injection while improving the electron blocking ability. Hence, a considerable enhancement of the output power can be obtained. Moreover, further investigations show that the thickness of graded LQB determine the band bending in the LQB and thus significantly suppress the electron leakage, eventually leading to a boosted output power. The thorough investigation on the LQB could pave the way towards the realization of efficient DUV LEDs of the future.
关键词： electron blocking layer,ultraviolet light-emitting diodes,light output power,polarization field,graded last quantum barrier
更新于2025-09-23 15:19:57
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Band engineering of III-nitride-based deep-ultraviolet light-emitting diodes: A review
摘要： III-nitride deep ultraviolet (DUV) light-emitting diodes (LEDs) are identified as the promising candidate for energy-efficient, environment-friendly and robust UV lighting source in the application of water/air purification, sterilization, and bio-sensing. However, the state-of-art DUV LED performance is far from satisfaction for commercialization owing to its low internal quantum efficiency, large current leakage and efficiency droop at high current injection, etc. Extensive efforts have been devoted to properly designing the band structures of such luminescent devices to enhance their output power. In this review, we summarize the recent progress on various energy band designs and engineering of DUV LEDs, with particular of interest is paid on the various approaches in band engineering of the electron-blocking layer, quantum well, quantum barrier and the implementation of many novel structures such as tunnel junctions, ultrathin quantum heterostructures to enhance their efficiency. Those inspirational approaches pave the way towards the next generation of greener and efficient UV sources for practical applications.
关键词： Quantum well,Quantum barrier,Deep ultraviolet light-emitting diode,Ultrathin quantum heterostructures,Band engineering,Electron-blocking layer,Tunnel junctions,III-nitride
更新于2025-09-19 17:13:59
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Investigating the Efficiency Droop of Nitride-Based Blue LEDs with Different Quantum Barrier Growth Rates
摘要： In this study, GaN-based blue InGaN/GaN light-emitting diodes (LEDs) with di?erent growth rates of the quantum barriers were fabricated and investigated. The LEDs with quantum barriers grown with a higher growth rate exhibit a lower leakage current and less non-radiative recombination centers in the multiple quantum wells (MQWs). Therefore, the LED with a higher barrier growth rate achieves a better light output power by 18.4% at 120 mA, which is attributed to weaker indium ?uctuation e?ect in the QWs. On the other hand, the localized states created by indium ?uctuation lead to a higher local carrier density, and Auger recombination in the QWs. Thus, the e?ciency droop ratio of the LEDs with a higher barrier growth rate was only 28.6%, which was superior to that with a lower barrier growth rate (39.3%).
关键词： and growth rate,nitride-based LEDs,e?ciency droop,quantum barrier
更新于2025-09-16 10:30:52
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Interplay between various active regions and the interband transition for AlGaN-based deep-ultraviolet light-emitting diodes to enable a reduced TM-polarized emission
摘要： Al-rich AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) have a low light extraction efficiency, especially when the emission wavelength is shorter than 280 nm, and this is partially because of the dominant transverse-magnetic polarized light. Our results show that the transverse-electric (TE) polarized light can be obtained even if the emission wavelength becomes even shorter by reducing the quantum well thickness. The ultrathin quantum well enables the enhanced TE-polarized emission that arises from the redistributed subbands for holes. On the contrary to the common belief, we observe a blueshift for the emission wavelength when the AlN composition in the quantum barrier increases. The internal quantum efficiency (IQE) for DUV LEDs with ultrathin quantum wells is no longer determined by the quantum-confined Stark effect, while quantum barrier with high AlN composition is vitally important to improve the electron injection efficiency and thus enhance the IQE.
关键词： quantum well,AlGaN,quantum barrier,internal quantum efficiency,deep-ultraviolet,TE-polarized emission,light-emitting diodes
更新于2025-09-12 10:27:22
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Carrier transport improvement in ZnO/MgZnO multiple-quantum-well ultraviolet light-emitting diodes by energy band modification on MgZnO barriers
摘要： Ultraviolet (UV) light-emitting diodes (LEDs) based on zinc oxide (ZnO) materials have been the subject of many investigations because of their potential applications. In this study, ZnO/MgZnO multiple-quantum-well UV LEDs with graded-composition barriers were developed and numerically analyzed. The simulation results demonstrate that an optimized LED with a Mg composition graded from 24% to 2% in each triangular barrier exhibits the highest internal quantum efficiency (IQE) (88.0%) at 200 A/cm2, showing a 31.3% increase compared with the conventional LED with square barriers. This enhancement is attributed to the modified energy band structures that improve the symmetry in carrier transportation and increase the radiative recombination rate in each ZnO quantum well, thus enhancing the IQE of the device. Additionally, the different band-offset ratios of the MgZnO/ZnO and InGaN/GaN heterojunctions, which lead to the different carrier transport and electroluminescence properties of the ZnO- and GaN-based LEDs, were discussed here, providing researchers new insights into device design of ZnO-based LEDs.
关键词： Numerical simulation,Quantum barrier,Carrier transport,Zinc oxide,Light-emitting diode
更新于2025-09-12 10:27:22