Article
Physics, Condensed Matter
Yang Wang, Bin Duan, Gaoqiang Deng, Ye Yu, Yunfei Niu, Jiaqi Yu, Haotian Ma, Zhifeng Shi, Baolin Zhang, Yuantao Zhang
Summary: In this study, blue-green InGaN/GaN multiple quantum wells were grown on SiC substrates by metal-organic chemical vapor deposition, and the influence of growth pressure on their structural and optical properties was investigated. It was found that increasing growth pressure nearly doubles the indium content in the MQWs and leads to distinct temperature-dependent optical behaviors. Furthermore, growth pressure significantly affects the structural characteristics of the MQWs, influencing surface morphology and defect density.
SUPERLATTICES AND MICROSTRUCTURES
(2021)
Article
Materials Science, Multidisciplinary
J. Mickevicius, K. Nomeika, M. Dmukauskas, A. Kadys, S. Nargelas, R. Aleksiejunas
Summary: The study shows that pulsed growth or increasing growth temperature can enhance the internal quantum efficiency of InGaN multiple quantum well structures. At low excitations, higher growth temperature can reduce point defect density and improve IQE, but the effect saturates at high excitations, while pulsed growth affects carrier recombination pathways.
Article
Engineering, Electrical & Electronic
Yu Yin, Renfeng Chen, Yiwei Duo, Rui He, Jiankun Yang, Xiaoli Ji, Hao Long, Junxi Wang, Tongbo Wei
Summary: In this study, we investigated the carrier recombination and transportation process in dual-wavelength InGaN/GaN multiple quantum wells Micro-LED arrays under piezo-phototronic effects. The results showed that external strain influenced the violet electroluminescence (EL) intensity, but had little effect on the blue EL emission. Additionally, reducing the size of Micro-LED resulted in a decrease in the enhancement obtained via the piezo-phototronic effect. The study also found that strain-induced interface polarized charges increased the wave function overlap of electron-hole pairs but reduced the injection of hole carriers in the blue quantum well.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2023)
Article
Materials Science, Multidisciplinary
Ying Zhao, Shengrui Xu, Ruoshi Peng, Jinjuan Du, Xiaomeng Fan, Hongchang Tao, Jincheng Zhang, Jinfeng Zhang, Lansheng Feng, Yue Hao
Summary: The study investigated InGaN/GaN multiple quantum wells (MQWs) based light-emitting diode (LED) structures grown on silicon carbide (SiC) substrates with and without sputtered AlN nucleation layer (NL). Results showed that using sputtered AlN NL improved GaN crystalline quality, surface morphology, and luminescence property of the LED structures.
Article
Engineering, Electrical & Electronic
M. Ikram Md Taib, M. A. Ahmad, E. A. Alias, A. Alhassan, I. A. Ajia, M. M. Muhammed, I. S. Roqan, S. P. DenBaars, J. S. Speck, S. Nakamura, N. Zainal
Summary: In-surfactant was introduced during the growth of high temperature GaN quantum barriers and GaN interlayer in InGaN/GaN green LEDs. Results showed that the introduction of In-surfactant improved LED growth, particularly in the GaN interlayer. It improved the morphology of the interlayer, allowed it to serve as a good surface growth, and effectively improved the multi-quantum wells. Moreover, the introduction of In-surfactant shifted the emission wavelength towards red, reduced the forward voltage of the LEDs, and allowed faster carrier decay lifetime.
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2023)
Article
Chemistry, Physical
Jishi Cui, Jianping Zhou, Hongdi Xiao
Summary: InGaN-based multiple quantum wells embedded in nanoporous GaN layers were fabricated using electrochemical etching to improve the photoluminescence (PL) strength of the InGaN/GaN stacking layers. Among the three etching methods tested, HNO3 etching resulted in the highest enhancement of the PL strength, which can be attributed to stress relaxation, light scattering and reflection, and resonant cavity-induced spontaneous emission. Annealing the nanopore walls in NH3 atmosphere further improved the light extraction efficiency of the multiple quantum wells.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Article
Optics
J. Mickevic, E. Valkiunaite, Z. Podlipskas, K. Nomeika, S. Nargelas, G. Tamulaitis, Y. C. Chow, S. Nakamura, J. S. Speck, C. Weisbuch, R. Aleksieju
Summary: The dynamics of two distinct bands in non-polar m-plane InGaN/GaN multiple quantum wells (MQWs) were investigated using PL, CL, and DT spectroscopy. The shift in peak emission wavelength with increasing excitation was caused by competition between these bands. DT measurements attributed the high-energy PL band to optical transitions between ground QW states, while the low-energy PL band was associated with recombination of localized carriers. CL measurements confirmed the dispersion of deep localized states and suggested small-scale disorder. PL measurements showed that localized states are highly sensitive to indium content and structural parameters. Temperature-dependent PL studies revealed strong carrier-phonon interaction.
JOURNAL OF LUMINESCENCE
(2023)
Article
Engineering, Electrical & Electronic
Feng Xie, Yufei Yao, Yan Gu, Zhijia Hu, Benli Yu, Guofeng Yang
Summary: A high-performance InGaN/GaN multiple quantum well p-i-n photodetector with patterned sapphire substrates was fabricated. The detector showed a low dark current density of <2.0 x 10(-10) A/cm(2) at -2 V bias voltage, with a high contrast ratio of photocurrent to dark current over 10(6). Furthermore, the peak responsivity reached 0.18 A/W at -10 V for a wavelength of 395 nm, corresponding to a maximum quantum efficiency of approximately 56%. In addition, the noise equivalent power (NEP) and normalized detectivity were 1.14 x 10(-11) W and 2.77 x 10(11) cm center dot Hz(0.5) center dot W-1, respectively. The high-performance of the photodetector is believed to be due to the high crystalline quality of the InGaN epilayer.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Physics, Applied
Johanna Meier, Patrick Haeuser, Christian Blumberg, Tim Smola, Werner Prost, Nils Weimann, Gerd Bacher
Summary: Site- and polarity-controlled core-shell InGaN/GaN nanorod LED structures were grown on Si(111) using metal organic vapor phase epitaxy. Uniform multiple quantum wells on polarization-free sidewalls were observed through scanning transmission electron microscope images. Spatially resolved photoluminescence mapping confirmed the emission at 3.0 eV from the polarization-free m-plane, with a fast recombination lifetime of about 490 ps at low temperatures. Quasi-resonant laser excitation demonstrated predominant radiative recombination at low excitation densities, while efficiency was decreased by Auger recombination and/or carrier leakage at high excitation densities.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Optics
Yuhao Ben, Feng Liang, Degang Zhao, Jing Yang, Zongshun Liu, Ping Chen
Summary: The use of InGaN instead of GaN as a quantum barrier layer can significantly reduce the threshold current of blue laser diodes, but the improvement in slope efficiency is limited due to an increase in leakage current. However, experimental results show a significant increase in slope efficiency by 34% in fabricated LDs using InGaN quantum barrier layers compared to those using GaN quantum barrier layers.
OPTICS AND LASER TECHNOLOGY
(2022)
Article
Chemistry, Physical
Chin Chyi Loo, Sha Shiong Ng, Wei Sea Chang
Summary: The recent progress in piezotronics and piezo-phototronics has revealed new methods for adjusting/enhancing the performance of GaN-based devices, and the photostrictive effect in GaN samples with InGaN/GaN MQWs can be elucidated through the combination of light-induced surface electric field and converse piezoelectric effect. The enhanced piezoelectric coefficient under laser illumination suggests the potential for adjustable photostrictive responses in optomechanical sensors/actuators by manipulating the strain state of MQWs.
Article
Materials Science, Multidisciplinary
Yufei Hou, Feng Liang, Degang Zhao, Ping Chen, Jing Yang, Zongshun Liu
Summary: The luminescence mechanism of inhomogeneous InGaN/GaN multiple quantum wells (MQWs) grown by MOCVD is studied. Fluctuations in layer thickness and In content of QWs lead to a deterioration of MQWs' quality. Temperature-dependent PL spectra show that the luminescence homogeneity of MQWs becomes worse with increasing well thickness. Theoretical calculations confirm the stronger electric field and wavelength redshift in wider QWs caused by the quantum confinement Stark effect.
RESULTS IN PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Jumpei Yamada, Ai Mizuno, Tatsuya Honda, Keigo Yoshida, Rie Togashi, Ichirou Nomura, Tomohiro Yamaguchi, Tohru Honda, Katsumi Kishino
Summary: This study investigated the growth behavior of Indium gallium nitride (InGaN)-based nanocolumn arrays and fabricated red emission nanocolumn micro-light emitting diodes (μ-LEDs). The internal structure of the InGaN/GaN superlattice (SL) layer under the multiple-quantum-well (MQW) active layers was evaluated using scanning transmission electron microscopy (STEM) analysis. It was found that the crystal plane at the top of the nanocolumn changed as the number of SL pairs increased, and the growth of the semipolar (10-11) plane InGaN active layers was observed. Red nanocolumn μ-LEDs with an φ12μm emission window were fabricated, achieving an external quantum efficiency of 1.01% at 51 A cm(-2).
Article
Chemistry, Applied
Dezhong Cao, Tongle Guan, Bo Wang, Yan Xu, Xiaohua Ma
Summary: The InGaN-based multiple quantum wells thin films were etched and transferred, showing enhanced and blue-shift photoluminescence emission compared to the original sample. The enhancement is attributed to improved crystalline quality and increased light extraction efficiency due to the structure of vertically aligned nanoporous InGaN/GaN. The blue-shift is caused by stress relaxation of MQWs and variable In content in InGaN layer.
MICROPOROUS AND MESOPOROUS MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Mandar A. Kulkarni, Hyesu Ryu, Hak-Jong Choi, Ameer Abdullah, Hamza Thaalbi, Fawad Tariq, Sang Hyun Lee, Hyungjun Lim, Sang-Wan Ryu
Summary: Gallium nitride (GaN) based low-dimensional optoelectronic devices, particularly InGaN/GaN multi-quantum wells (MQWs) based on nanostructured GaN, have potential applications in display technology due to their tunable bandgap and small size. Researchers are exploring the growth of MQWs on non-polar planes to mitigate polarization-induced effects and improve emission characteristics and device performance.
Article
Chemistry, Multidisciplinary
Aadil Waseem, Muhammad Ali Johar, Mostafa Afifi Hassan, Indrajit Bagal, Ameer Abdullah, Jun-Seok Ha, June Key Lee, Sang-Wan Ryu
Summary: The crystallographic orientation control of GaN nanowires was achieved by varying the indium composition in the Ga-Au alloy catalyst, with the alloy droplet size determining the density of the nanowires. Increasing the In composition inside the alloy catalyst shifted the crystallographic orientation of the GaN nanowires from m- to c-axis.
Article
Materials Science, Multidisciplinary
Santosh S. Patil, Muhammad Ali Johar, Mostafa Afifi Hassan, Aadil Waseem, Indrajit Bagal, Diksha E. Shinde, Sang-Wan Ryu
Summary: The novel PEC cell design based on GaN/ZnO/CoPi heterojunction cascade showed enhanced photoelectrocatalytic activity towards oxygen evolution reaction, with ZnO nanostructures and CoPi modification playing key roles in improving charge transfer and reaction kinetics. This work paves the way for developing high-performance photoelectrodes utilizing underexplored GaN and other heterostructures.
MATERIALS CHEMISTRY AND PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Ameer Abdullah, Muhammad Ali Johar, Aadil Waseem, Indrajit Bagal, Mostafa Afifi Hassan, June Key Lee, Sang-Wan Ryu
Summary: In this study, a noble metal/semiconductor composite photoanode was synthesized by depositing Au NPs on gallium nitride (GaN), resulting in a significant enhancement in photocurrent density. Additionally, improvements in STH conversion efficiency were achieved through efficient light harvesting and effective extraction of hot electrons and charge carrier collection.
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS
(2022)
Article
Chemistry, Physical
Ameer Abdullah, Aadil Waseem, Indrajit V. Bagal, Muhammad Ali Johar, Mandar A. Kulkarni, June Key Lee, Sang-Wan Ryu
Summary: The efficient fabrication of photoanodes provides a new approach to improve the PEC water splitting efficiency. Deposition of Au nanoparticles on GaN nanowires surface is an effective method to enhance performance.
ACS APPLIED ENERGY MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Aadil Waseem, Indrajit Bagal, Ameer Abdullah, Mandar A. Kulkarni, Hamza Thaalbi, Jun-Seok Ha, June Key Lee, Sang-Wan Ryu
Summary: In this study, a high-performance, flexible, and highly stable piezoelectric nanogenerator was prepared by directly growing the Mg-doped semi-insulating GaN nanowires on a metal foil. The nanogenerator showed high output power density and was able to be tested and monitored under various conditions.
Article
Physics, Applied
J. Lee, Y. C. Chiu, M. A. Johar, C. Bayram
Summary: Cubic GaN epitaxy on large-area U-grooved silicon (100) dies is achieved by metalorganic chemical vapor deposition, exhibiting excellent structural and optical properties. Further improvement in internal quantum efficiency of cubic GaN can be achieved through selective etching.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Applied
Indrajit Bagal, Maheswari Arunachalam, Ameer Abdullah, Aadil Waseem, Mandar A. Kulkarni, Soon Hyung Kang, Sang-Wan Ryu
Summary: This study presents strategic improvements in the PEC water splitting performance of ZnO nanowires by nitrogen doping and the core-shell deposition of a NiOOH cocatalyst. Nitrogen doping enhances visible light absorption and suppresses the recombination of photogenerated carriers. NiOOH-deposited N-doped ZnO nanowire photoanodes show significantly improved photostability and photocurrent density.
JOURNAL OF ENERGY CHEMISTRY
(2022)
Article
Chemistry, Physical
Indrajit Bagal, Aadil Waseem, Ameer Abdullah, Mandar A. Kulkarni, Jun-Seok Ha, Sang-Wan Ryu
Summary: We report the sequential fabrication of a three-dimensional hierarchical structure of Al2O3-passivated-CdS-anchored high-quality ZnO nanowire (NW) for photoelectrochemical water splitting. The optimized CdS/Si-ZnO HNWs show significant enhancements in photoconversion efficiency and photocurrent density compared to bare Si-ZnO HNWs. Furthermore, the photostability and photocorrosion resistance are improved by passivating the CdS/ZnO-Si HNWs using ultrathin Al2O3. The hierarchical NW photoanodes synergistically improve photocurrent and photostability, allowing for facile integration of II-VI materials with Si for next-generation energy applications.
JOURNAL OF ALLOYS AND COMPOUNDS
(2022)
Review
Materials Science, Multidisciplinary
Aadil Waseem, Zhongjie Ren, Hsien-Chih Huang, Kristen Nguyen, Xihang Wu, Xiuling Li
Summary: This review discusses the recent progress in epitaxial growth of beta-Ga2O3 films and highlights challenges in obtaining high growth rate, low defects, and high carrier mobilities. Compared with other methods, MOCVD offers a wider growth window and precursor selection option. The choice of MOCVD precursors, nucleation, and adsorption/desorption/diffusion of adatoms on substrate surfaces can affect growth defects, background impurity incorporation, and carrier mobilities.
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
(2023)
Article
Nanoscience & Nanotechnology
Ameer Abdullah, Aadil Waseem, Indrajit Bagal, Muhammad Ali Johar, Mandar A. Kulkarni, Hamza Thaalbi, Jun-Seok Ha, June Key Lee, Sang-Wan Ryu
Summary: In this study, we investigated the influence of changing the number of InGaN/GaN quantum well pairs, optical bandgap tuning, and plasmonic coupling of Au nanoparticles (NPs) with multiquantum wells (MQWs) in photoelectrochemical (PEC) water splitting. MQWs showed a 2-fold improvement in photocurrent density and ABPE% compared to reference GaN at zero bias. Tuning the optical band gap by varying the growth temperature of MQWs has also been shown to influence the performance of PEC water splitting. Au NP/MQWs significantly enhanced photocurrent density and stability, with 80% photocurrent retention after 13.9 hours.
ACS APPLIED NANO MATERIALS
(2023)
Article
Chemistry, Physical
Indrajit V. Bagal, Seongmoon Jun, Minho Choi, Ameer Abdullah, Aadil Waseem, Seonghun Ahn, Mandar A. Kulkarni, Yong-Hoon Cho, Sang-Wan Ryu
Summary: In this study, shape-modulated ZnO nanowires (NWs) were synthesized and their role in achieving competent photoelectrochemical water splitting (PEC-WS) performance was investigated. The carrier dynamics of smooth (s-) and beaded ZnO NW (b-ZnO NW) photoanodes were analyzed using time-resolved, temperature-controlled photoluminescence spectroscopy. The enhanced PEC-WS performance with b-ZnO NWs was attributed to reduced surface recombination states, improved crystallinity, and enhanced carrier lifetime.
APPLIED SURFACE SCIENCE
(2023)
Article
Engineering, Electrical & Electronic
Aadil Waseem, Ameer Abdullah, Indrajit Bagal, Jun-Seok Ha, June Key Lee, Sang-Wan Ryu
Summary: This study proposes SA and RA mechanoreceptors based on GaN nanowire arrays, which can mimic the tactile perception principles of human skin. The designed e-skin can simulate both static and dynamic pressure signals, and can quickly respond to various pressure stimuli, making it practical for applications.
NPJ FLEXIBLE ELECTRONICS
(2022)