Article
Nanoscience & Nanotechnology
K. Khan, S. Diez, Kai Sun, C. Wurm, U. K. Mishra, E. Ahmadi
Summary: This study reports the observation of self-assembled InGaN/(In)GaN superlattice structure in InGaN film grown on N-polar GaN substrate, with varying In content in each layer depending on growth temperature. By increasing the substrate temperature, a periodic structure was achieved, offering a new pathway for designing and fabricating electronic and optoelectronic devices with enhanced performance.
Article
Physics, Applied
Abu Bashar Mohammad Hamidul Islam, Tae Kyoung Kim, Dong-Soo Shin, Jong-In Shim, Joon Seop Kwak
Summary: This study investigates the effect of current stress on InGaN/GaN multiple-quantum-well flip-chip blue micro light-emitting diodes (mu-LEDs) and reveals the mechanisms of defect aggregation and generation that cause changes in the optoelectronic performance of the devices. The aging test shows that the improvement in crystal quality due to defect aggregation initially enhances the light output power and external quantum efficiency (EQE), but the generation of sidewall point defects eventually leads to performance degradation. The findings highlight the importance of both defect aggregation and generation in understanding the degradation mechanisms of mu-LEDs.
APPLIED PHYSICS LETTERS
(2022)
Article
Optics
Katarzyna Pieniak, Witold Trzeciakowski, Grzegorz Muziol, Anna Kafar, Marcin Siekacz, Czeslaw Skierbiszewski, Tadeusz Suski
Summary: The study examined electroluminescence from In0.17Ga0.83N/GaN quantum wells of LEDs and LDs, finding a transition from ground-states recombination to excited states recombination with increasing QW width. The effect is accompanied by partial or complete screening of the built-in electric field with increasing driving current, which was studied using a high pressure method. Investigations were supported by simulations of the variation with driving current of electron and hole wavefunctions overlap affecting the recombination channel and built-in electric field.
Article
Physics, Applied
Ah Hyun Park, Seungjae Baek, Go Bong Choi, Yoong Ahm Kim, Jinsub Lim, Tae Hoon Seo
Summary: In this study, green light emitting diodes (LEDs) with Au nanoclusters in a micro-hole patterned p-GaN layer (ANCs-MHPP) were demonstrated to have higher internal quantum efficiencies and faster decay times compared to conventional green LEDs. The remarkable opto-electronic performance of green LEDs with ANCs-MHPP is attributed to exciton-surface plasmon coupling and surface texturing effect caused by the micro-hole patterned p-GaN layer.
APPLIED PHYSICS LETTERS
(2021)
Article
Optics
Jacob J. Ewing, Cheyenne Lynsky, Matthew S. Wong, Feng Wu, Yi Chao Chow, Pavel Shapturenka, Michel Iza, Shuji Nakamura, Steven P. Denbaars, James S. Speck
Summary: This article studied the method of achieving highly efficient long-wavelength InGaN LEDs through V-defect engineering, which utilized naturally occurring V-defects for lateral injection and improved the external quantum efficiency.
Article
Engineering, Electrical & Electronic
Feifan Xu, Guobin Wang, Tao Tao, Zhe Zhuang, Qi-Ang Yan, Ting Zhi, Zili Xie, Bin Liu, Wengang Bi, Ke Xu, Rong Zhang
Summary: As state-of-the-art displays advance, micro light-emitting diodes (Micro-LEDs) are emerging as a pivotal player due to their small pixel size and efficiency. By investigating Micro-LEDs with different quantum structures, we have shown significant improvement in optoelectronic properties at low current injection. Thinning the InGaN quantum well enhances the electron-hole wave function overlap, increasing radiation efficiency, while a thinner GaN barrier achieves uniform carrier distribution and reduced quantum confinement stark effect (QCSE) in multiple quantum wells (MQWs). Optimized Micro-LEDs exhibit uniform emission and high brightness, making them suitable for full-color displays when combined with quantum dots (QDs).
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Chemistry, Physical
Do-Yeong Shin, Taehwan Kim, Ozgun Akyuz, Hilmi Volkan Demir, In-Hwan Lee
Summary: This study presents an improved efficiency design for white LEDs by integrating blue nanorod LEDs with green and red-emitting perovskite nanocrystal films. The design utilizes the localized surface plasmon effect of Ag@SiO2 nanoparticles to enhance the photoluminescence intensity of blue LEDs, while the high-power blue LED backlight improves the perovskite photoluminescence intensity. The resulting white LED with Ag@SiO2 nanoparticle-embedded nanorods demonstrates a 62% increase in photoluminescence intensity compared to planar white LEDs.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Physics, Applied
Nicola Roccato, Francesco Piva, Carlo De Santi, Matteo Buffolo, Camille Haller, Jean-Francois Carlin, Nicolas Grandjean, Gaudenzio Meneghesso, Enrico Zanoni, Matteo Meneghini
Summary: The study found that the indium content in InGaN light-emitting diodes has a significant impact on defect density and degradation rate. Results indicate the important role of indium in favoring the incorporation of point defects.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Luming Yu, Lei Wang, Peilong Yang, Zhibiao Hao, Jiadong Yu, Yi Luo, Changzheng Sun, Bing Xiong, Yanjun Han, Jian Wang, Hongtao LI, Lai Wang
Summary: This study successfully self-assembled high-indium-composition quantum dots using metal-organic vapor phase epitaxy, and investigated the growth mechanism. The fabricated micro-LEDs showed a blueshift in the emission wavelength and demonstrated different external quantum efficiencies for different sizes.
OPTICAL MATERIALS EXPRESS
(2022)
Article
Optics
Zhe Zhuang, Daisuke Iida, Martin Velazquez-Rizo, Kazuhiro Ohkawa
Summary: The study introduced a method for fabricating ultra-small InGaN μLEDs, successfully realizing different shapes of green μLEDs. It was found that as the size of the μLED decreases, the series resistance and turn-on voltage increase, while the light output power density and external quantum efficiency also improve.
Article
Materials Science, Multidisciplinary
Liwen Cheng, Xingyu Lin, Zhenwei Li, Da Yang, Jiayi Zhang, Jundi Wang, Jiarong Zhang, Yuru Jiang
Summary: InGaN LEDs with IGIT barriers have higher light output power, lower turn-on voltage, and less efficiency droop compared to LEDs with conventional GaN and InGaN barriers. These improvements are a result of the appropriately designed energy band diagram, which enhances hole injection efficiency and electron confinement.
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY
(2021)
Article
Optics
Zhen Huang, Renchun Tao, Duo Li, Zhiwei Rao, Zexing Yuan, Tai Li, Zhaoying Chen, Ye Yuan, Junjie Kang, Zhiwen Liang, Qi Wang, Pengfei Tian, Bo Shen, Xinqiang Wang
Summary: A GaN-based blue micro-LED array with InGaN barriers has been fabricated, showing a two-fold increase in light output power compared to a conventional device. Additionally, an improved data transmission rate of up to 1.50 Gbps has been achieved in a visible light communication prototype.
Article
Computer Science, Information Systems
Yong Huang, Zhiyou Guo, Miao Zhang, Dan Xiang
Summary: This study investigated the impact of different AlxGa1-xN/GaN superlattice electron blocking layer structures on the performance of GaN-based UV LEDs through simulation analysis, revealing that double-peak SL-EBL significantly improves the internal quantum efficiency of the LEDs.
Article
Physics, Applied
Zhen Huang, Renchun Tao, Duo Li, Zexing Yuan, Tai Li, Zhaoying Chen, Ye Yuan, Junjie Kang, Zhiwen Liang, Qi Wang, Pengfei Tian, Bo Shen, Xinqiang Wang
Summary: In this work, a method is proposed to improve the modulation bandwidth of green mu-LEDs by enhancing p-type conductivity. The polarization-induced p-type doping with graded AlGaN significantly enhances the conductivity of the p-type layer, leading to improved light output power and modulation bandwidth.
APPLIED PHYSICS LETTERS
(2022)
Article
Optics
Yu-Ming Huang, Chun-Yen Peng, Wen-Chien Miao, Hsin Chiang, Tzu-Yi Lee, Yun-Han Chang, Konthoujam James Singh, Z. Daisuke Iida, Ray-Hua Horng, Chi-Wai Chow, Chien-Chung Lin, Kazuhiro Ohkawa, Shih-Chen Chen, Hao-Chung Kuo
Summary: In this study, a high-efficiency InGaN red micro-LED is presented, which incorporates superlattice structure, atomic layer deposition passivation, and a distributed Bragg reflector. It exhibits a maximum external quantum efficiency of 5.02% and a low efficiency droop at an injection current density of 112 A/cm(2). The fast carrier dynamics in the InGaN is characterized, and a high modulation bandwidth of 271 MHz is achieved by a 6x 25-μm-sized micro-LED array with a data transmission rate of 350 Mbit/s at a high injection current density of 2000 A/cm(2). The technology holds great promise for full-color micro-displays and high-speed visible light communication applications based on monolithic InGaN micro-LED technologies.
PHOTONICS RESEARCH
(2022)
Article
Chemistry, Multidisciplinary
Guangcai Hu, Bin Xu, Aifei Wang, Yan Guo, Jiajing Wu, Faheem Muhammad, Wen Meng, Chuying Wang, Shiqi Sui, Yao Liu, Yacong Li, Ye Zhang, Yugang Zhou, Zhengtao Deng
Summary: This study successfully synthesized highly emissive organic-inorganic manganese halide perovskites using a one-pot solution-based method, demonstrating their potential application in blue light pumped white light-emitting diodes with superior white light emission quality.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Engineering, Electrical & Electronic
Yan Guo, Sai Pan, Danfeng Pan, Chaojun Xu, Yugang Zhou, Rong Zhang, Youdou Zheng
Summary: The Mg/Al bilayer achieves high-reflectivity ohmic contact for n-GaN, but annealing temperature significantly affects the contact resistivity and reflectivity. Annealing below 300 degrees Celsius maintains high reflectivity, while excessively high temperatures deteriorate the ohmic characteristics.
IEEE PHOTONICS TECHNOLOGY LETTERS
(2021)
Article
Physics, Applied
Zhenhua Li, Pengfei Shao, Yaozheng Wu, Genjun Shi, Tao Tao, Zili Xie, Peng Chen, Yugang Zhou, Xiangqian Xiu, Dunjun Chen, Bin Liu, Ke Wang, Youdou Zheng, Rong Zhang, Tsungtse Lin, Li Wang, Hideki Hirayama
Summary: The high Al composition AlGaN epilayers were grown on AlN/sapphire templates using plasma assisted molecular beam epitaxy. Three growth regions were identified and AlGaN growth diagrams were summarized. The experimental critical thicknesses were observed increasing as Al composition increases, with a bowing parameter of 1.1 eV determined by optical absorption edges.
JAPANESE JOURNAL OF APPLIED PHYSICS
(2021)
Article
Engineering, Electrical & Electronic
Zhigang Jia, Xiaodong Hao, Taiping Lu, Hailiang Dong, Zhiwei Jia, Aiqin Zhang, Shufang Ma, Jian Liang, Wei Jia, Tianbao Li, Bingshe Xu
Summary: Different period numbers of InGaN/GaN quantum wells were grown and characterized, showing a relationship between strain, VPs density, In-rich QDs formation, and internal quantum efficiency.
MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING
(2021)
Article
Engineering, Electrical & Electronic
Xuyang Liu, Sihao Chen, Hang Chen, Yingbin Qiu, Chao Liu
Summary: In this study, GaN-based vertical Schottky barrier diodes (SBDs) with embedded floating islands (FIs) were reported. The incorporation of FI structure broke the theoretical limits of unipolar vertical GaN devices by homogenizing the electric field distribution. Analytical models and TCAD simulations were used to establish and verify the behavior of FI SBDs. Parametric optimization led to an improved figure of merit (FOM) compared to traditional SBDs.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2022)
Article
Engineering, Electrical & Electronic
Mengran Liu, Chao Liu
Summary: In this paper, an Al-composition-increasing AlGaN layer (ACI-AlGaN) was proposed to enhance the carrier injection ability of DUV LEDs. The positive sheet charges at the interface between the last quantum barrier and the p-type electron blocking layer were eliminated, reducing electron leakage and promoting hole injection. The proposed DUV LED structure exhibited a 45.7% increase in EQE, while maintaining a stable forward voltage.
IEEE PHOTONICS JOURNAL
(2022)
Article
Optics
Yongchen Ji, Mengran Liu, Chao Liu
Summary: This work proposes a design for AlGaN deep-ultraviolet light-emitting diodes (DUV LEDs) that incorporates embedded p-i-n junctions to compensate for the polarization-induced electric field in the multi-quantum well region. The embedded junctions increase the overlap of hole and electron wave functions, improving the radiative recombination rates and the efficiency of DUV LEDs. The proposed structure provides an alternative approach to achieve efficient DUV LEDs.
Article
Computer Science, Information Systems
Jian Yin, Sihao Chen, Hang Chen, Shuti Li, Houqiang Fu, Chao Liu
Summary: This study reports on gallium nitride (GaN) vertical trench junction barrier Schottky (TJBS) diodes and analyzes the effects of key design parameters on the device characteristics. By optimizing the design parameters, the breakdown voltage of TJBS diodes can be significantly improved. Additionally, an analytical model was developed to explain the physical mechanism behind the forward conduction behavior.
Article
Optics
Sai Pan, Kuili Chen, Yan Guo, Yugang Zhou, Rong Zhang, Youdou Zheng
Summary: This study investigates methods to enhance the light output efficiency and thermal stability of DUV LEDs. Ag nanodots and Al/Mg reflective mirrors are used to increase the light output power. Inserting a Ti barrier layer prevents the degradation of the ohmic contact. Experimental and simulated results highlight the importance of the ohmic contact for the hole-injection efficiency of DUV LEDs.
Article
Physics, Applied
Nan Jin, Yugang Zhou, Yan Guo, Sai Pan, Rong Zhang, Youdou Zheng
Summary: This work presents the fabrication and analysis of high-reflectivity Ag nanodot (AgND)/Mg/Al Ohmic contacts on both p-GaN and n-GaN. The contacts showed low specific resistance and excellent thermal stability. X-ray photoelectron spectroscopy and x-ray diffraction measurements were conducted to investigate the contact mechanisms. The results suggest that this contact scheme can improve the density of GaN-based ICs and micro-LEDs, as well as enhance the light output efficiency of GaN-based LEDs.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
Mingyan Wang, Yuanjie Lv, Heng Zhou, Zuokai Wen, Peng Cui, Chao Liu, Zhaojun Lin
Summary: This study investigates bias-dependent electron and thermal transport using the electrothermal Monte Carlo (MC) simulation. The simulation is based on velocity-field characteristics obtained using a self-consistent iterative method. The results show good agreement with previously extracted experiments, and a proposed model based on polar optical phonon (POP) scattering and polarization Coulomb field (PCF) scattering explains the bias-dependent electron transport. The accuracy of the MC simulation is confirmed by the agreement between experimental results and simulated current-voltage characteristics.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Chemistry, Physical
Sheng Lin, Tingjun Lin, Wenliang Wang, Chao Liu, Yao Ding
Summary: In this work, a distinguished GaN-based photodetector with Te/metal electrodes is constructed on a sapphire substrate. The metal-like properties of tellurium generate an inherent electric field at the interface between Te and GaN, greatly reducing the carrier transport barrier and promoting the photoresponse of GaN. This Te-enhanced GaN-based PD shows high responsivity, detectivity, and quantum efficiency, as well as improved response time.
Article
Materials Science, Multidisciplinary
Wentao Tian, Mengran Liu, Shuti Li, Chao Liu
Summary: In this study, a thin AlGaN insertion layer was introduced between the AlGaN electron blocking layer (EBL) and p-AlGaN hole supplier to enhance the hole injection efficiency of DUV LEDs by regulating the energy band at the p-EBL/p-AlGaN interface. It was found that the insertion layer with an Al composition of 45% effectively improved the EQE of DUV LEDs by 40.5% and reduced efficiency droop by 65.5%. This design strategy provides an effective approach to enhance the hole injection efficiency for AlGaN-based DUV LEDs.
OPTICAL MATERIALS EXPRESS
(2023)
Article
Materials Science, Multidisciplinary
Mengran Liu, Wentao Tian, Chao Liu
Summary: Insufficient hole injection and current nonuniformity caused by the p-AlGaN hole injection layer are addressed by proposing an Al-linearly-decreasing AlGaN PN junction to replace the conventional p-AlGaN HIL with a constant Al component. The proposed structure enhances hole injection efficiency and improves current uniformity by modulating the barrier height and resistance in the p-AlGaN HIL. The DUV LED with the proposed ALD AlGaN PN junction structure achieves enhanced EQE and improved current uniformity, showing promise for high-performance DUV LEDs.
OPTICAL MATERIALS EXPRESS
(2023)
Article
Engineering, Electrical & Electronic
Heng Wang, Sihao Chen, Hang Chen, Chao Liu
Summary: Gallium nitride (GaN) has shown great potential for power electronic devices, particularly in the vertical device topology, thanks to its wider energy band gap and higher carrier mobility. However, the reverse leakage issues in GaN-based vertical SBDs have challenged their performance. To address this issue, various device architectures have been developed to enhance their breakdown voltage and reduce reverse leakage current.
IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY
(2022)
