1
|
Liu Z, Lu Y, Cao H, Maciel Garcia GI, Liu T, Tang X, Xiao N, Aguileta Vazquez R, Nong M, Li X. Etching-free pixel definition in InGaN green micro-LEDs. LIGHT, SCIENCE & APPLICATIONS 2024; 13:117. [PMID: 38782914 PMCID: PMC11116531 DOI: 10.1038/s41377-024-01465-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 03/31/2024] [Accepted: 04/24/2024] [Indexed: 05/25/2024]
Abstract
The traditional plasma etching process for defining micro-LED pixels could lead to significant sidewall damage. Defects near sidewall regions act as non-radiative recombination centers and paths for current leakage, significantly deteriorating device performance. In this study, we demonstrated a novel selective thermal oxidation (STO) method that allowed pixel definition without undergoing plasma damage and subsequent dielectric passivation. Thermal annealing in ambient air oxidized and reshaped the LED structure, such as p-layers and InGaN/GaN multiple quantum wells. Simultaneously, the pixel areas beneath the pre-deposited SiO2 layer were selectively and effectively protected. It was demonstrated that prolonged thermal annealing time enhanced the insulating properties of the oxide, significantly reducing LED leakage current. Furthermore, applying a thicker SiO2 protective layer minimized device resistance and boosted device efficiency effectively. Utilizing the STO method, InGaN green micro-LED arrays with 50-, 30-, and 10-µm pixel sizes were manufactured and characterized. The results indicated that after 4 h of air annealing and with a 3.5-μm SiO2 protective layer, the 10-µm pixel array exhibited leakage currents density 1.2 × 10-6 A/cm2 at -10 V voltage and a peak on-wafer external quantum efficiency of ~6.48%. This work suggests that the STO method could become an effective approach for future micro-LED manufacturing to mitigate adverse LED efficiency size effects due to the plasma etching and improve device efficiency. Micro-LEDs fabricated through the STO method can be applied to micro-displays, visible light communication, and optical interconnect-based memories. Almost planar pixel geometry will provide more possibilities for the monolithic integration of driving circuits with micro-LEDs. Moreover, the STO method is not limited to micro-LED fabrication and can be extended to design other III-nitride devices, such as photodetectors, laser diodes, high-electron-mobility transistors, and Schottky barrier diodes.
Collapse
Affiliation(s)
- Zhiyuan Liu
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Yi Lu
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Haicheng Cao
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Glen Isaac Maciel Garcia
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Tingang Liu
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Xiao Tang
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Na Xiao
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Raul Aguileta Vazquez
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Mingtao Nong
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia
| | - Xiaohang Li
- Advanced Semiconductor Laboratory, Electrical and Computer Engineering Program, CEMSE Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia.
| |
Collapse
|
2
|
Cameron D, Coulon PM, Fairclough S, Kusch G, Edwards PR, Susilo N, Wernicke T, Kneissl M, Oliver RA, Shields PA, Martin RW. Core-Shell Nanorods as Ultraviolet Light-Emitting Diodes. NANO LETTERS 2023; 23:1451-1458. [PMID: 36748796 PMCID: PMC9951243 DOI: 10.1021/acs.nanolett.2c04826] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 01/31/2023] [Indexed: 06/18/2023]
Abstract
Existing barriers to efficient deep ultraviolet (UV) light-emitting diodes (LEDs) may be reduced or overcome by moving away from conventional planar growth and toward three-dimensional nanostructuring. Nanorods have the potential for enhanced doping, reduced dislocation densities, improved light extraction efficiency, and quantum wells free from the quantum-confined Stark effect. Here, we demonstrate a hybrid top-down/bottom-up approach to creating highly uniform AlGaN core-shell nanorods on sapphire repeatable on wafer scales. Our GaN-free design avoids self-absorption of the quantum well emission while preserving electrical functionality. The effective junctions formed by doping of both the n-type cores and p-type caps were studied using nanoprobing experiments, where we find low turn-on voltages, strongly rectifying behaviors and significant electron-beam-induced currents. Time-resolved cathodoluminescence measurements find short carrier liftetimes consistent with reduced polarization fields. Our results show nanostructuring to be a promising route to deep-UV-emitting LEDs, achievable using commercially compatible methods.
Collapse
Affiliation(s)
- Douglas Cameron
- Department
of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, Glasgow G4 0NG, United Kingdom
| | - Pierre-Marie Coulon
- Department
of Electrical & Electronic Engineering, University of Bath, Bath BA2 7AY, United Kingdom
- Centre
de Recherche sur l’Hétéro-Epitaxie et ses Applications
(CRHEA)−Centre National de la Recherche Scientifique (CNRS), Rue Bernard Grégory, 06560 Valbonne, France
| | - Simon Fairclough
- Department
of Materials Science and Metallurgy, University
of Cambridge, CB3 OFS Cambridge, United Kingdom
| | - Gunnar Kusch
- Department
of Materials Science and Metallurgy, University
of Cambridge, CB3 OFS Cambridge, United Kingdom
| | - Paul R. Edwards
- Department
of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, Glasgow G4 0NG, United Kingdom
| | - Norman Susilo
- Institute
of Solid State Physics, Technische Universität
Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
| | - Tim Wernicke
- Institute
of Solid State Physics, Technische Universität
Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
| | - Michael Kneissl
- Institute
of Solid State Physics, Technische Universität
Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
| | - Rachel A. Oliver
- Department
of Materials Science and Metallurgy, University
of Cambridge, CB3 OFS Cambridge, United Kingdom
| | - Philip A. Shields
- Department
of Electrical & Electronic Engineering, University of Bath, Bath BA2 7AY, United Kingdom
| | - Robert W. Martin
- Department
of Physics, Scottish Universities Physics Alliance (SUPA), University of Strathclyde, Glasgow G4 0NG, United Kingdom
| |
Collapse
|
3
|
AlGaN Quantum Disk Nanorods with Efficient UV-B Emission Grown on Si(111) Using Molecular Beam Epitaxy. NANOMATERIALS 2022; 12:nano12142508. [PMID: 35889730 PMCID: PMC9319290 DOI: 10.3390/nano12142508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 07/20/2022] [Accepted: 07/20/2022] [Indexed: 11/17/2022]
Abstract
AlGaN nanorods have attracted increasing amounts of attention for use in ultraviolet (UV) optoelectronic devices. Here, self-assembled AlGaN nanorods with embedding quantum disks (Qdisks) were grown on Si(111) using plasma-assisted molecular beam epitaxy (PA-MBE). The morphology and quantum construction of the nanorods were investigated and well-oriented and nearly defect-free nanorods were shown to have a high density of about 2 × 1010 cm−2. By controlling the substrate temperature and Al/Ga ratio, the emission wavelengths of the nanorods could be adjusted from 276 nm to 330 nm. By optimizing the structures and growth parameters of the Qdisks, a high internal quantum efficiency (IQE) of the AlGaN Qdisk nanorods of up to 77% was obtained at 305 nm, which also exhibited a shift in the small emission wavelength peak with respect to the increasing temperatures during the PL measurements.
Collapse
|
4
|
Dvoretckaia L, Gridchin V, Mozharov A, Maksimova A, Dragunova A, Melnichenko I, Mitin D, Vinogradov A, Mukhin I, Cirlin G. Light-Emitting Diodes Based on InGaN/GaN Nanowires on Microsphere-Lithography-Patterned Si Substrates. NANOMATERIALS 2022; 12:nano12121993. [PMID: 35745332 PMCID: PMC9230727 DOI: 10.3390/nano12121993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 12/19/2022]
Abstract
The direct integration of epitaxial III-V and III-N heterostructures on Si substrates is a promising platform for the development of optoelectronic devices. Nanowires, due to their unique geometry, allow for the direct synthesis of semiconductor light-emitting diodes (LED) on crystalline lattice-mismatched Si wafers. Here, we present molecular beam epitaxy of regular arrays n-GaN/i-InGaN/p-GaN heterostructured nanowires and tripods on Si/SiO2 substrates prepatterned with the use of cost-effective and rapid microsphere optical lithography. This approach provides the selective-area synthesis of the ordered nanowire arrays on large-area Si substrates. We experimentally show that the n-GaN NWs/n-Si interface demonstrates rectifying behavior and the fabricated n-GaN/i-InGaN/p-GaN NWs-based LEDs have electroluminescence in the broad spectral range, with a maximum near 500 nm, which can be employed for multicolor or white light screen development.
Collapse
Affiliation(s)
- Liliia Dvoretckaia
- Department of Physics, Alferov University, Khlopina 8/3, 194021 St. Petersburg, Russia; (L.D.); (V.G.); (A.M.); (G.C.)
| | - Vladislav Gridchin
- Department of Physics, Alferov University, Khlopina 8/3, 194021 St. Petersburg, Russia; (L.D.); (V.G.); (A.M.); (G.C.)
- Institute of Physics, Saint Petersburg State University, Universitetskaya Emb. 7/9, 199034 St. Petersburg, Russia;
| | - Alexey Mozharov
- Institute of Physics, Saint Petersburg State University, Universitetskaya Emb. 7/9, 199034 St. Petersburg, Russia;
| | - Alina Maksimova
- Department of Physics, Alferov University, Khlopina 8/3, 194021 St. Petersburg, Russia; (L.D.); (V.G.); (A.M.); (G.C.)
| | - Anna Dragunova
- Department of Physics, National Research University Higher School of Economics, Kantemirovskaya 3/1 A, 194100 St. Petersburg, Russia; (A.D.); (I.M.)
| | - Ivan Melnichenko
- Department of Physics, National Research University Higher School of Economics, Kantemirovskaya 3/1 A, 194100 St. Petersburg, Russia; (A.D.); (I.M.)
| | - Dmitry Mitin
- Department of Chemistry, ITMO University, Lomonosova 9, 197101 St. Petersburg, Russia; (D.M.); (A.V.)
| | - Alexandr Vinogradov
- Department of Chemistry, ITMO University, Lomonosova 9, 197101 St. Petersburg, Russia; (D.M.); (A.V.)
| | - Ivan Mukhin
- Department of Physics, Alferov University, Khlopina 8/3, 194021 St. Petersburg, Russia; (L.D.); (V.G.); (A.M.); (G.C.)
- Department of Chemistry, ITMO University, Lomonosova 9, 197101 St. Petersburg, Russia; (D.M.); (A.V.)
- Higher School of Engineering Physics, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia
- Correspondence:
| | - Georgy Cirlin
- Department of Physics, Alferov University, Khlopina 8/3, 194021 St. Petersburg, Russia; (L.D.); (V.G.); (A.M.); (G.C.)
- Institute of Physics, Saint Petersburg State University, Universitetskaya Emb. 7/9, 199034 St. Petersburg, Russia;
| |
Collapse
|
5
|
Wang D, Liu X, Fang S, Huang C, Kang Y, Yu H, Liu Z, Zhang H, Long R, Xiong Y, Lin Y, Yue Y, Ge B, Ng TK, Ooi BS, Mi Z, He JH, Sun H. Pt/AlGaN Nanoarchitecture: Toward High Responsivity, Self-Powered Ultraviolet-Sensitive Photodetection. NANO LETTERS 2021; 21:120-129. [PMID: 33320006 DOI: 10.1021/acs.nanolett.0c03357] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Energy-saving photodetectors are the key components in future photonic systems. Particularly, self-powered photoelectrochemical-type photodetectors (PEC-PDs), which depart completely from the classical solid-state junction device, have lately intrigued intensive interest to meet next-generation power-independent and environment-sensitive photodetection. Herein, we construct, for the first time, solar-blind PEC PDs based on self-assembled AlGaN nanostructures on silicon. Importantly, with the proper surface platinum (Pt) decoration, a significant boost of photon responsivity by more than an order of magnitude was achieved in the newly built Pt/AlGaN nanoarchitectures, demonstrating strikingly high responsivity of 45 mA/W and record fast response/recovery time of 47/20 ms without external power source. Such high solar-blind photodetection originates from the unparalleled material quality, fast interfacial kinetics, as well as high carrier separation efficiency which suggests that embracement of defect-free wide-bandgap semiconductor nanostructures with appropriate surface decoration offers an unprecedented opportunity for designing future energy-efficient and large-scale optoelectronic systems on a silicon platform.
Collapse
Affiliation(s)
- Danhao Wang
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Xin Liu
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Shi Fang
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Chen Huang
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Yang Kang
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Huabin Yu
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Zhongling Liu
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Haochen Zhang
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Ran Long
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Yujie Xiong
- School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230029, P.R. China
| | - Yangjian Lin
- Institute of Physical Science and Information Technology, Anhui University, Hefei 230029, P.R. China
| | - Yang Yue
- Institute of Physical Science and Information Technology, Anhui University, Hefei 230029, P.R. China
| | - Binghui Ge
- Institute of Physical Science and Information Technology, Anhui University, Hefei 230029, P.R. China
| | - Tien Khee Ng
- Computer, Electrical, and Mathematical Sciences, and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Boon S Ooi
- Computer, Electrical, and Mathematical Sciences, and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Zetian Mi
- Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, United States
| | - Jr-Hau He
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR 999077, P.R. China
| | - Haiding Sun
- School of Microelectronics, University of Science and Technology of China, Hefei 230029, P.R. China
| |
Collapse
|
6
|
Liu M, Tan L, Zhou B, Li L, Mi Z, Li CJ. Group-III Nitrides Catalyzed Transformations of Organic Molecules. Chem 2021. [DOI: 10.1016/j.chempr.2020.09.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
7
|
Jain B, Velpula RT, Tumuna M, Bui HQT, Jude J, Pham TT, le TV, Hoang AV, Wang R, Nguyen HPT. Enhancing the light extraction efficiency of AlInN nanowire ultraviolet light-emitting diodes with photonic crystal structures. OPTICS EXPRESS 2020; 28:22908-22918. [PMID: 32752544 DOI: 10.1364/oe.396788] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 06/23/2020] [Indexed: 06/11/2023]
Abstract
In this paper, AlInN nanowire ultraviolet light-emitting diodes (LEDs) with emission at ∼299 nm have been successfully demonstrated. We have further studied the light extraction properties of these nanowire LEDs using photonic crystal structures with square and hexagonal lattices of nanowires. The light extraction efficiency (LEE) of the periodic nanowire LED arrays was found to be significantly increased as compared to random nanowire LEDs. The LEEs reach ∼ 56%, and ∼ 63% for the square and hexagonal photonic crystal-based nanowire structures, respectively. Moreover, highly transverse-magnetic polarized emission was observed with dominant vertical light emission for the AlInN nanowire ultraviolet LEDs.
Collapse
|
8
|
Khayrudinov V, Remennyi M, Raj V, Alekseev P, Matveev B, Lipsanen H, Haggren T. Direct Growth of Light-Emitting III-V Nanowires on Flexible Plastic Substrates. ACS NANO 2020; 14:7484-7491. [PMID: 32437132 PMCID: PMC7315631 DOI: 10.1021/acsnano.0c03184] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 05/21/2020] [Indexed: 05/27/2023]
Abstract
Semiconductor nanowires are routinely grown on high-priced crystalline substrates as it is extremely challenging to grow directly on plastics and flexible substrates due to high-temperature requirements and substrate preparation. At the same time, plastic substrates can offer many advantages such as extremely low price, light weight, mechanical flexibility, shock and thermal resistance, and biocompatibility. We explore the direct growth of high-quality III-V nanowires on flexible plastic substrates by metal-organic vapor phase epitaxy (MOVPE). We synthesize InAs and InP nanowires on polyimide and show that the fabricated NWs are optically active with strong light emission in the mid-infrared range. We create a monolithic flexible nanowire-based p-n junction device on plastic in just two fabrication steps. Overall, we demonstrate that III-V nanowires can be synthesized directly on flexible plastic substrates inside a MOVPE reactor, and we believe that our results will further advance the development of the nanowire-based flexible electronic devices.
Collapse
Affiliation(s)
- Vladislav Khayrudinov
- Department
of Electronics and Nanoengineering, Micronova,
Aalto University, P.O. Box 13500, Espoo FI-00076, Finland
| | | | - Vidur Raj
- Department
of Electronic Materials Engineering, Research School of Physics and
Engineering, The Australian National University, Canberra, ACT 2601, Australia
| | | | | | - Harri Lipsanen
- Department
of Electronics and Nanoengineering, Micronova,
Aalto University, P.O. Box 13500, Espoo FI-00076, Finland
| | - Tuomas Haggren
- Department
of Electronics and Nanoengineering, Micronova,
Aalto University, P.O. Box 13500, Espoo FI-00076, Finland
- Department
of Electronic Materials Engineering, Research School of Physics and
Engineering, The Australian National University, Canberra, ACT 2601, Australia
| |
Collapse
|
9
|
AlGaN Nanowires for Ultraviolet Light-Emitting: Recent Progress, Challenges, and Prospects. MICROMACHINES 2020; 11:mi11020125. [PMID: 31979274 PMCID: PMC7074201 DOI: 10.3390/mi11020125] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 01/19/2020] [Accepted: 01/22/2020] [Indexed: 12/12/2022]
Abstract
In this paper, we discuss the recent progress made in aluminum gallium nitride (AlGaN) nanowire ultraviolet (UV) light-emitting diodes (LEDs). The AlGaN nanowires used for such LED devices are mainly grown by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD); and various foreign substrates/templates have been investigated. Devices on Si so far exhibit the best performance, whereas devices on metal and graphene have also been investigated to mitigate various limitations of Si substrate, e.g., the UV light absorption. Moreover, patterned growth techniques have also been developed to grow AlGaN nanowire UV LED structures, in order to address issues with the spontaneously formed nanowires. Furthermore, to reduce the quantum confined Stark effect (QCSE), nonpolar AlGaN nanowire UV LEDs exploiting the nonpolar nanowire sidewalls have been demonstrated. With these recent developments, the prospects, together with the general challenges of AlGaN nanowire UV LEDs, are discussed in the end.
Collapse
|
10
|
Liudi Mulyo A, Rajpalke MK, Vullum PE, Weman H, Kishino K, Fimland BO. The influence of AlN buffer layer on the growth of self-assembled GaN nanocolumns on graphene. Sci Rep 2020; 10:853. [PMID: 31964934 PMCID: PMC6972738 DOI: 10.1038/s41598-019-55424-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 11/18/2019] [Indexed: 02/07/2023] Open
Abstract
GaN nanocolumns were synthesized on single-layer graphene via radio-frequency plasma-assisted molecular beam epitaxy, using a thin migration-enhanced epitaxy (MEE) AlN buffer layer as nucleation sites. Due to the weak nucleation on graphene, instead of an AlN thin-film we observe two distinguished AlN formations which affect the subsequent GaN nanocolumn growth: (i) AlN islands and (ii) AlN nanostructures grown along line defects (grain boundaries or wrinkles) of graphene. Structure (i) leads to the formation of vertical GaN nanocolumns regardless of the number of AlN MEE cycles, whereas (ii) can result in random orientation of the nanocolumns depending on the AlN morphology. Additionally, there is a limited amount of direct GaN nucleation on graphene, which induces non-vertical GaN nanocolumn growth. The GaN nanocolumn samples were characterized by means of scanning electron microscopy, transmission electron microscopy, high-resolution X-ray diffraction, room temperature micro-photoluminescence, and micro-Raman measurements. Surprisingly, the graphene with AlN buffer layer formed using less MEE cycles, thus resulting in lower AlN coverage, has a lower level of nitrogen plasma damage. The AlN buffer layer with lowest AlN coverage also provides the best result with respect to high-quality and vertically-aligned GaN nanocolumns.
Collapse
Affiliation(s)
- Andreas Liudi Mulyo
- Department of Electronic Systems, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway.,Department of Engineering and Applied Sciences, Sophia University, 102-8554, Tokyo, Japan
| | - Mohana K Rajpalke
- Department of Electronic Systems, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway.,Microsoft Quantum Materials Lab, Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
| | | | - Helge Weman
- Department of Electronic Systems, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway
| | - Katsumi Kishino
- Department of Engineering and Applied Sciences, Sophia University, 102-8554, Tokyo, Japan. .,Sophia Nanotechnology Research Center, Sophia University, 102-8554, Tokyo, Japan. .,Sophia University, 102-8554, Tokyo, Japan.
| | - Bjørn-Ove Fimland
- Department of Electronic Systems, Norwegian University of Science and Technology (NTNU), NO-7491, Trondheim, Norway.
| |
Collapse
|
11
|
Alwadai N, Ajia IA, Janjua B, Flemban TH, Mitra S, Wehbe N, Wei N, Lopatin S, Ooi BS, Roqan IS. Catalyst-Free Vertical ZnO-Nanotube Array Grown on p-GaN for UV-Light-Emitting Devices. ACS APPLIED MATERIALS & INTERFACES 2019; 11:27989-27996. [PMID: 31343859 DOI: 10.1021/acsami.9b06195] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One-dimensional (1D) structures-based UV-light-emitting diode (LED) has immense potential for next-generation applications. However, several issues related to such devices must be resolved first, such as expensive material and growth methods, complicated fabrication process, efficiency droop, and unavoidable metal contamination due to metal catalyst that reduces device efficiency. To overcome these obstacles, we have developed a novel growth method for obtaining a high-quality hexagonal, well-defined, and vertical 1D Gd-doped n-ZnO nanotube (NT) array deposited on p-GaN films and other substrates by pulsed laser deposition. By adopting this approach, the desired high optical and structural quality is achieved without utilizing metal catalyst. Transmission electron microscopy measurements confirm that gadolinium dopants in the target form a transparent in situ interface layer to assist in vertical NT formation. Microphotoluminescence (PL) measurements of the NTs reveal an intense ZnO band edge emission without a defect band, indicating high quality. Carrier dynamic analysis via time-resolved PL confirms that the emission of n-ZnO NTs/p-GaN LED structure is dominated significantly by the radiative recombination process without efficiency droop when high carrier density is injected optically. We developed an electrically pumped UV Gd-doped ZnO NTs/GaN LED as a proof of concept, demonstrating its high internal quantum efficiency (>65%). The demonstrated performance of this cost-effective UV LED suggests its potential application in large-scale device production.
Collapse
Affiliation(s)
- Norah Alwadai
- Department of Physics, College of Sciences , Princess Nourah Bint Abdulrahman University (PNU) , Riyadh 11671 , Saudi Arabia
| | | | | | - Tahani H Flemban
- Department of Physics, College of Science , Imam Abdulrahman Bin Faisal University (IAU) , Dammam 31441 , Saudi Arabia
| | | | | | | | | | | | | |
Collapse
|
12
|
Brubaker MD, Genter KL, Roshko A, Blanchard PT, Spann BT, Harvey TE, Bertness KA. UV LEDs based on p-i-n core-shell AlGaN/GaN nanowire heterostructures grown by N-polar selective area epitaxy. NANOTECHNOLOGY 2019; 30:234001. [PMID: 30776789 PMCID: PMC7679058 DOI: 10.1088/1361-6528/ab07ed] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Ultraviolet light-emitting diodes fabricated from N-polar AlGaN/GaN core-shell nanowires (NWs) with p-i-n structure produced electroluminescence at 365 nm with ∼5× higher intensities than similar GaN homojunction LEDs. The improved characteristics were attributed to localization of spontaneous recombination to the NW core, reduction of carrier overflow losses through the NW shell, and elimination of current shunting. Poisson-drift-diffusion modeling indicated that a shell Al mole fraction of x = 0.1 in Al x Ga1-x N effectively confines electrons and injected holes to the GaN core region. AlGaN overcoat layers targeting this approximate Al mole fraction were found to possess a low-Al-content tip and high-Al-content shell, as determined by scanning transmission electron microscopy. Photoluminescence spectroscopy further revealed the actual Al mole fraction to be NW diameter-dependent, where the tip and shell compositions converged towards the nominal flux ratio for large diameter NWs.
Collapse
Affiliation(s)
- Matt D Brubaker
- Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States of America
| | | | | | | | | | | | | |
Collapse
|
13
|
Zhang L, Guo YN, Yan JC, Wu QQ, Wei XC, Wang JX, Li JM. Deep ultraviolet light-emitting diodes with improved performance via nanoporous AlGaN template. OPTICS EXPRESS 2019; 27:4917-4926. [PMID: 30876101 DOI: 10.1364/oe.27.004917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 01/19/2019] [Indexed: 06/09/2023]
Abstract
We report the performance enhancement of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) using AlGaN nanoporous template (NPT). The NPT was fabricated by the electrochemical etching method and served as the dislocation filtering layer and strain relieving layer. The n-AlGaN laterally regrown on NPT showed reduced dislocation density and mitigated compressive strain comparing with that on the as-grown template (AGT). A 23% improvement of internal quantum efficiency was achieved for the multiple quantum wells thereon. Moreover, the nanopores in the NPT transformed into elongated air voids during high temperature growth process, which could facilitate the escaping of photons by scattering and thus improve the light extraction efficiency. As a consequence, the DUV LED based on NPT demonstrated an increase of the light outpower by 50% at 20 mA than that on AGT.
Collapse
|
14
|
Zhao C, Ebaid M, Zhang H, Priante D, Janjua B, Zhang D, Wei N, Alhamoud AA, Shakfa MK, Ng TK, Ooi BS. Quantified hole concentration in AlGaN nanowires for high-performance ultraviolet emitters. NANOSCALE 2018; 10:15980-15988. [PMID: 29897082 DOI: 10.1039/c8nr02615g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
p-Type doping in wide bandgap and new classes of ultra-wide bandgap materials has long been a scientific and engineering problem. The challenges arise from the large activation energy of dopants and high densities of dislocations in materials. We report here, a significantly enhanced p-type conduction using high-quality AlGaN nanowires. For the first time, the hole concentration in Mg-doped AlGaN nanowires is quantified. The incorporation of Mg into AlGaN was verified by correlation with photoluminescence and Raman measurements. The open-circuit potential measurements further confirmed the p-type conductivity, while Mott-Schottky experiments measured a hole concentration of 1.3 × 1019 cm-3. These results from photoelectrochemical measurements allow us to design prototype ultraviolet (UV) light-emitting diodes (LEDs) incorporating the AlGaN quantum-disks-in-nanowire and an optimized p-type AlGaN contact layer for UV-transparency. The ∼335 nm LEDs exhibited a low turn-on voltage of 5 V with a series resistance of 32 Ω, due to the efficient p-type doping of the AlGaN nanowires. The bias-dependent Raman measurements further revealed the negligible self-heating of devices. This study provides an attractive solution to evaluate the electrical properties of AlGaN, which is applicable to other wide bandgap nanostructures. Our results are expected to open doors to new applications for wide and ultra-wide bandgap materials.
Collapse
Affiliation(s)
- Chao Zhao
- King Abdullah University of Science and Technology (KAUST), Photonics Laboratory, Thuwal 23955-6900, Saudi Arabia.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Yang Y, Zong H, Ma C, Wei T, Li J, Zhang J, Li M, Pan C, Hu X. Self-selection mechanism of Fabry-Pérot micro/nanoscale wire cavity for single-mode lasing. OPTICS EXPRESS 2017; 25:21025-21036. [PMID: 29041512 DOI: 10.1364/oe.25.021025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 08/11/2017] [Indexed: 06/07/2023]
Abstract
Developing micro/nanoscale wire (MNW) lasers with single-mode operation is critical for realizing their practical applications, however, most reported MNW lasers operate in multi-modes, because lacking of mode selection mechanisms. In this work, a simple and direct way to realize stable, single-mode MNW laser without complicated micro/nano-manipulation was demonstrated. We have found and proved that the position of the active region plays a key role in determining the lasing mode of MNW lasers, which can be used to realize single-mode lasing in MNWs. We propose self-selection mechanism of Fabry-Pérot MNW cavity for single-mode lasing due to location-dependent field distribution in MNWs, which is characterized by suppressing the multiple longitudinal mode oscillation of the MNW laser. GaN MNW lasers with different lengths and diameters have been fabricated, verifying the self-selection mechanism of the cavity experimentally. Moreover, we demonstrate the single-mode, room temperature optically pumped MNW laser with an extremely low threshold (~40 kW/cm2) in condition of appropriate cavity length, opening an opportunity to realize stable single-mode, low-threshold MNW laser for easy integration in constructing micro/nanoscale photonic and optoelectronic circuits and devices.
Collapse
|
16
|
|
17
|
Janjua B, Sun H, Zhao C, Anjum DH, Wu F, Alhamoud AA, Li X, Albadri AM, Alyamani AY, El-Desouki MM, Ng TK, Ooi BS. Self-planarized quantum-disks-in-nanowires ultraviolet-B emitters utilizing pendeo-epitaxy. NANOSCALE 2017; 9:7805-7813. [PMID: 28290591 DOI: 10.1039/c7nr00006e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The growth of self-assembled, vertically oriented and uniform nanowires (NWs) has remained a challenge for efficient light-emitting devices. Here, we demonstrate dislocation-free AlGaN NWs with spontaneous coalescence, which are grown by plasma-assisted molecular beam epitaxy on an n-type doped silicon (100) substrate. A high density of NWs (filling factor >95%) was achieved under optimized growth conditions, enabling device fabrication without planarization using ultraviolet (UV)-absorbing polymer materials. UV-B (280-320 nm) light-emitting diodes (LEDs), which emit at ∼303 nm with a narrow full width at half maximum (FWHM) (∼20 nm) of the emission spectrum, are demonstrated using a large active region ("active region/NW length-ratio" ∼50%) embedded with 15 stacks of AlxGa1-xN/AlyGa1-yN quantum-disks (Qdisks). To improve the carrier injection, a graded layer is introduced at the AlGaN/GaN interfaces on both p- and n-type regions. This work demonstrates a viable approach to easily fabricate ultra-thin, efficient UV optoelectronic devices on low-cost and scalable silicon substrates.
Collapse
Affiliation(s)
- B Janjua
- King Abdullah University of Science and Technology (KAUST), Photonics Laboratory, Thuwal 23955-6900, Saudi Arabia.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|