Article
Engineering, Electrical & Electronic
Jiahao Yin, Xiaoshuai An, Liang Chen, Jing Li, Jianan Wu, Yumeng Luo, Qing Wang, Hongyu Yu, Kwai Hei Li
Summary: The study focused on monolithic integrated photodetectors (PDs) in InGaN/GaN LEDs for monitoring LED intensity fluctuations. Through simulation and experiments, it was found that placing the PD in the center of the LED resulted in a 58% increase in detected photocurrent with minimal impact on the LED emission profile compared to placing the PD at the edge. Encapsulating the LED-PD device with yellow phosphor enabled white light emission, and the on-chip PD showed similar sensing behaviors to an external Si-based photodiode. The optimal monolithic PD design offered comparable sensing capabilities, compactness, insensitivity to ambient lighting, and minimal influence on the LED emission profile, making it suitable for real-time monitoring of LED intensity in practical and scientific lighting applications.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2021)
Article
Physics, Applied
Ding Wang, Ping Wang, Minming He, Jiangnan Liu, Shubham Mondal, Mingtao Hu, Danhao Wang, Yuanpeng Wu, Tao Ma, Zetian Mi
Summary: In this Letter, fully epitaxial ScAlN/AlGaN/GaN based ferroelectric high electron mobility transistors (HEMTs) were demonstrated using molecular beam epitaxy. The fabricated ferroelectric gate HEMTs showed counterclockwise hysteretic transfer curves with a wide threshold voltage tuning range, a large ON/OFF ratio, and reconfigurable output characteristics. The high quality ferroelectric gate stack and effective ferroelectric polarization coupling lead to improved subthreshold performance. These results provide fundamental insight into the ferroelectric polarization coupling and threshold tuning processes in ferroelectric nitride heterostructures and have promising applications in next-generation electronics.
APPLIED PHYSICS LETTERS
(2023)
Article
Engineering, Electrical & Electronic
Kui Pan, Kaixin Zhang, Liying Deng, Chang Lin, Yang Li, Hengshan Liu, Fan Zhang, Junyang Nie, Jie Sun, Anjun Su, Nianrui Chen, Jun Zhou, Qun Yan, Tailiang Guo
Summary: This article reports on the fabrication of monolithically and vertically integrated LED-on-FET devices on a new GaN epitaxial structure. The designed device structure and fabrication process are simple, and it shows high reliability and low interconnect resistance. The integrated LED efficiently emits specific wavelength light under voltage and gate voltage control.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Optics
Longheng Qi, Xu Zhang, Wing Cheung Chong, Kei May Lau
Summary: This paper demonstrates a monolithic full-color micro-LED microdisplay with a resolution of 423 pixels per inch by integrating a blue GaN-on-Si display module and a quantum dots photoresist color conversion module. The result is a full-color micro-LED display with a wide color gamut and high brightness. The prototype shows potential scalability and low-cost volume production of high-resolution full-color micro-LED microdisplays.
PHOTONICS RESEARCH
(2023)
Article
Optics
Qifeng Lyu, Huaxing Jiang, Kei May Lau
Summary: The study demonstrates the first integration of monolithically integrated UV LEDs and visible-blind UV PDs on Si substrate, achieving high sensitivity and low dark current. By optimizing the structure and materials, it offers potential for various applications with high-performance UV PDs and LEDs.
Article
Engineering, Electrical & Electronic
Jingyu Shen, Chao Yang, Liang Jing, Jingwei Guo, Ping Li, Hao Wu, Shengdong Hu
Summary: In this study, an enhancement mode p-GaN gate HEMT with selective regrowth and strain engineering has been proposed. The device shows improved 2DEG density and surface electric field distribution, leading to significant improvements in ON-resistance and breakdown voltage.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Review
Chemistry, Multidisciplinary
Paramaguru Ganesan, Hoi Nok Tsao, Peng Gao
Summary: Organic light-emitting transistors (OLETs) combine the switching functionality of field-effect transistors (FETs) with the light-emitting characteristics of organic light-emitting diodes (OLEDs) to simplify device architecture for flat panel and flexible display technology. Key tactics include improving electrode design, utilizing vertical architecture for short channel lengths and high aperture ratios, and incorporating high–k dielectric materials to enhance device performance.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Ajeet Singh, Biao Yuan, Md. Habibur Rahman, Hanjun Yang, Angana De, Jee Yung Park, Shuchen Zhang, Libai Huang, Arun Mannodi-Kanakkithodi, Timothy J. Pennycook, Letian Dou
Summary: This study reports the epitaxial core-shell heterostructures of Pb-free double perovskites grown around Pb perovskite 2D crystals. The growth of the Pb-free shell at 45 degrees on the (100) surface of the lead perovskite core is observed in all Pb-free cases. In-depth structural analysis confirms the growth of the Pb-free shell along the [110] direction of the Pb perovskite. Interestingly, the diffusion of halide anions in Pb-free 2D perovskites is significantly suppressed compared to Pb-based 2D perovskites.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Optics
Jiabin Yan, Bolun Jia, Yongjin Wang
Summary: This study presents a novel monolithically integrated voltage-controlled metal-oxide-semiconductor field effect transistor (MOSFET)-LED device with good dimming and switching capabilities, achieved without external metal interconnection. The innovative structure and fabrication process simplify the device structure and production.
Article
Nanoscience & Nanotechnology
Andreas Liudi Mulyo, Anjan Mukherjee, Ida Marie Hoiaas, Lyubomir Ahtapodov, Tron Arne Nilsen, Havard Hem Toftevaag, Per Erik Vullum, Katsumi Kishino, Helge Weman, Bjorn-Ove Fimland
Summary: This study successfully demonstrates the fabrication of flip-chip ultraviolet light-emitting diodes based on self-assembled GaN/AlGaN nanocolumns, using single-layer graphene as both a growth substrate and a transparent conducting electrode. The high crystalline quality of the nanocolumns and the presence of intrinsic GaN quantum disk are confirmed through detailed electron microscopy characterization. The optical emission characteristics reveal the absence of defect-related yellow emission and the presence of blue-shifted emission, attributed to quantum confinement and strain effects.
ACS APPLIED NANO MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Yoshinobu Kawaguchi, Kentaro Murakawa, Motohisa Usagawa, Yuuta Aoki, Kazuma Takeuchi, Takeshi Kamikawa
Summary: We propose a novel laser diode fabrication process to produce GaN-based edge emitting LDs with a cavity length of 100 mu m and cleaved facets. The process involves growing epitaxial LD layers on a Si substrate using the epitaxial lateral overgrowth (ELO) technique. The unique configuration of the ELO layers generates anisotropic tensile strain, enabling automatic cleavage of the laser facets without a breaking process. This fabrication process has the potential to create low energy consumption III-nitride LDs for mobile applications like augmented-reality glasses.
CRYSTAL GROWTH & DESIGN
(2023)
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
Engineering, Electrical & Electronic
Ang Li, Yi Shen, Ziqian Li, Yinchao Zhao, Ivona Z. Mitrovic, Huiqing Wen, Sang Lam, Wen Liu
Summary: This letter demonstrates a monolithic voltage reference circuit based on AlGaN/GaN HEMTs technology. The circuit consists of two transistors and is capable of generating a predictable reference voltage with high stability and fast initialization under wide ranges of supply voltage and temperature.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Materials Science, Multidisciplinary
Shaoqian Lu, Guohao Yu, Yingfei Sun, Xu Yuan, Zhongkai Du, Bingliang Zhang, Lu Wang, Yu Li, Dongdong Wu, Zengli Huang, Zhongming Zeng, Xulei Qin, Baoshun Zhang
Summary: In this article, a method of nitrogen plasma treatment is proposed to achieve normally off p-GaN/AlGaN/GaN high-electron-mobility transistors, and the related mechanism is proposed. The nitrogen plasma treatment depletes holes in the p-GaN layer and changes the surface characteristics, resulting in the formation of a 2D electron gas at the AlGaN/GaN interface. The device shows enhanced performance with improved threshold voltage, on/off ratio, and maximum drain current.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2023)
Article
Optics
Jinpeng Huang, Zelin Hu, Xiang Gao, Yi Xu, Liancheng Wang
Summary: This study proposes a single-chip micro-LED display technology with unidirectional emission through the integration of a resonant cavity and metasurface, which can achieve efficient naked-eye 3D display with a wide viewing angle and multiple viewpoints. The research promotes the application of GaN-based micro-LEDs in displays, especially in 3D displays.
Article
Engineering, Electrical & Electronic
Renqiang Zhu, Huaxing Jiang, Chak Wah Tang, Kei May Lau
Summary: In this study, the enhancement of ON and OFF-state performance in vertical GaN trench MOSFETs is reported through process optimization. The ON-state performance was improved by reducing MOS channel interface charges with a cleaning process, while the OFF-state performance was enhanced by suppressing the electric field in the gate dielectric near the bottom of the gate trench. High-performance quasi-vertical GaN trench MOSFETs with low specific ON-resistance and high breakdown voltage were demonstrated.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Optics
Peian Li, Xu Zhang, Longheng Qi, Kei May Lau
Summary: In this study, a full-color micro-display is demonstrated by bonding an InGaN blue/green dual-wavelength LED array and an AlGaInP red LED array. The micro-display, with a high brightness and wide color gamut, shows the potential of a cost-effective and high-performance full-color LED micro-display for virtual reality and augmented reality devices.
Review
Optics
Yu Han, Hyundai Park, John Bowers, Kei May Lau
Summary: This article reviews the recent advances in on-chip light sources integrated onto mainstream Si platforms and discusses four different integration technologies. It introduces the basic concepts, focuses on recent progress, and discusses the research challenges and opportunities associated with each technology.
ADVANCES IN OPTICS AND PHOTONICS
(2022)
Article
Physics, Applied
Renqiang Zhu, Huaxing Jiang, Chak Wah Tang, Kei May Lau
Summary: This study reports on the use of vertical GaN trench MOSFETs with step-graded channel doping, which achieved a better trade-off between I-ON, R-ON, and V-th compared to conventional devices with uniform channel doping.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Jie Li, Ying Xue, Liying Lin, Zengshan Xing, Kam Sing Wong, Kei May Lau
Summary: In this study, we achieved the fabrication of high-quality InGaAs/InP quantum well lasers on commercially available silicon-on-insulator substrates using selective epitaxy, while achieving efficient coupling with Si waveguides with the lateral aspect ratio trapping technique. The experimental results demonstrated low threshold pulsed lasing on the fabricated micro-ring lasers at room temperature, which is a crucial step towards electrically pumped lasers at telecom band as well as fully integrated Si-photonics.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2022)
Article
Optics
Ying Xue, Yu Han, Yi Wang, Jie LI, Jingyi Wang, Zunyue Zhang, Xinlun Cai, Hon Ki Tsang, Kei May Lau
Summary: This article demonstrates the seamless integration of high-performance III-V photodetectors on SOI wafers and their intimate coupling with Si waveguides. The integrated devices exhibit low dark current, high photocurrent, large responsivities, and a wide detection wavelength range. High-speed measurements also reveal the capability for fast data communication.
Article
Optics
Longheng Qi, Xu Zhang, Wing Cheung Chong, Kei May Lau
Summary: This paper demonstrates a monolithic full-color micro-LED microdisplay with a resolution of 423 pixels per inch by integrating a blue GaN-on-Si display module and a quantum dots photoresist color conversion module. The result is a full-color micro-LED display with a wide color gamut and high brightness. The prototype shows potential scalability and low-cost volume production of high-resolution full-color micro-LED microdisplays.
PHOTONICS RESEARCH
(2023)
Article
Physics, Applied
Jie Huang, Qi Lin, Wei Luo, Liying Lin, Kei May Lau
Summary: The study found that the defect density of GaAs/Si templates could be significantly reduced with optimized thermal cycle annealing and dislocation filter layers, leading to lower surface roughness. Additionally, optically pumped InP quantum dot micro-disk lasers fabricated on these templates exhibited excellent performance with room-temperature continuous-wave lasing and ultra-low lasing thresholds.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Applied
Jie Li, Ying Xue, Zhao Yan, Yu Han, Kei May Lau
Summary: To achieve fully integrated silicon photonics, reliable III-V light sources that can efficiently couple with Si/SiN waveguides are crucial. A selective regrowth scheme was developed on a monolithic InP/SOI platform to construct on-chip lasers that can be efficiently coupled with Si/SiN waveguides. Strong photoluminescence emission at the telecom band was obtained on both growth templates, demonstrating the potential for multi-wavelength emission on the same chip. The regrowth method provides a promising solution for the monolithic integration of III-V on-chip lasers on Si.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Optics
Qi Lin, Jie Huang, Liying Lin, Wei Luo, Wen Gu, Kei May Lau
Summary: This article reports on the continuous wave lasing of 980nm electrically pumped quantum well lasers directly grown on silicon, and compares them with lasers grown on other substrates. The results show that although lasers grown on silicon have slightly higher threshold current, it still demonstrates a promising step towards realizing quantum well lasers on silicon.
Article
Optics
Xuetong Zhou, Ying Xue, Fan Ye, Ziyao Feng, Yuan Li, Xiankai Sun, Kei May Lau, Hon Ki Tsang
Summary: We propose and validate a new approach for high coupling efficiency (CE) grating couplers (GCs) in the lithium niobate on insulator photonic integration platform. Enhanced CE is achieved by increasing the grating strength using a high refractive index polysilicon layer on the GC. The optical cavity formed in the vertical direction enhances the CE of the waveguide GC, and simulations predict a CE of -1.40 dB while the experimentally measured CE is -2.20 dB with a 3-dB bandwidth of 81 nm from 1592 nm to 1673 nm. The high CE GC is achieved without using bottom metal reflectors or requiring the etching of the lithium niobate material.
Article
Engineering, Electrical & Electronic
Junmin Jiang, Xu Zhang, Xun Liu, Zhaojun Liu, Liusheng Sun, Shing Hin Yuen, Wing Cheung Chong, Wing-Hung Ki, C. Patrick Yue, Kei May Lau
Summary: This paper demonstrates a fully-integrated active matrix light-emitting diode (AMLED) micro-display system. The system consists of a 36 x 64 AMLED array chip based on GaN-on-Silicon epilayers and a silicon driving chip integrating an on-chip hybrid voltage regulator, pixel drivers, and peripheral circuits. The system achieves high pixel density and can operate directly with a battery without any external passive components.
IEEE JOURNAL ON EMERGING AND SELECTED TOPICS IN CIRCUITS AND SYSTEMS
(2023)
Article
Engineering, Electrical & Electronic
Yu Zhang, Yitian Gu, Jiaxiang Chen, Yitai Zhu, Baile Chen, Huaxing Jiang, Kei May Lau, Xinbo Zou
Summary: The OFF-state stress-induced threshold voltage instability and dynamic ON-resistance of GaN MOSHEMT with ZrO2 gate dielectric are investigated. Electron emission at the ZrO2/AlGaN interface is found to cause the threshold voltage shift. The activation energies of emission and capture are extracted by threshold voltage transient spectroscopy. Under OFF-state drain-source bias stressing, the drain current decreases despite the negative shift of threshold voltage, which is related to electron capture in the access region. The results suggest that high-quality ZrO2 is an attractive option for the gate dielectric of GaN MOSHEMTs in power switching electronics.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Optics
Longheng Qi, Peian Li, Xu Zhang, Ka Ming Wong, Kei May Lau
Summary: A prototype of full-color micro-LED micro-display with a pixel density of 391 ppi is demonstrated using InGaN/AlGaInP heterogeneous integration. This display shows the feasibility and prospects of high brightness, good color performance, and high-resolution micro-LED micro-displays in future metaverse applications.
LIGHT-SCIENCE & APPLICATIONS
(2023)
Article
Engineering, Electrical & Electronic
Yu Zhang, Lihua Xu, Yitian Gu, Haowen Guo, Huaxing Jiang, Kei May Lau, Xinbo Zou
Summary: This comprehensive study focuses on the dynamic characteristics of GaN MISHEMT with a 5nm-thick in-situ SiNx dielectric. The study examines the effects of both negative and positive gate bias on threshold voltage instability and finds a slight shift in threshold voltage associated with traps at the insulator/AlGaN interface and in the dielectric layer. Pulsed I-V measurements reveal small current collapse and low enhancement of dynamic R-on for zero quiescent drain bias, with an increased dynamic R-on/static R-on ratio identified at a drain quiescent bias of 20V. The study also observes additional current collapse in hard switching-on operation, caused by energetic hot electrons accelerated by drain-source electrical field during the off-to-on step. In summary, the use of a 5nm thin in-situ SiNX layer in GaN MISHEMT results in stabilized threshold voltage, a low dynamic R-on/static R-on ratio, and suppressed current collapse.
IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY
(2022)
