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Nanomaterials
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(Al, Ga)N-Based Nanostructures for UV-C Optoelectronics
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(Al, Ga)N-Based Nanostructures for UV-C Optoelectronics

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanophotonics Materials and Devices".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 3623

Special Issue Editor

Dr. Valentin Jmerik

E-Mail Website
Guest Editor
Centre of Nanoheterostructure Physics, Ioffe Institute, 26 Politekhnicheskaya, 194021 St. Petersburg, Russia
Interests: plasma-assised molecular beam epitaxy; nanoheterostructures; III-Nitrides; UV optoeletronics; Monolayer-thick GaN/AlN quantum wells
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

AlGaN-based ultraviolet (UV-C) optoelectronics in the 220–280 nm wavelength range, despite twenty years of successful development, still remains an area in which the efficiency and output power of UV-C emitters are inferior to the parameters of low-pressure mercury arc UV-C lamps (253.7nm) and semiconductor LEDs operating in the visible and UV-A ranges. The performance of UV-C optoelectronic devices especially deteriorates when operating wavelengths become shorter than 250 nm, which are necessary for their new applications, including instruments for in vivo disinfection, new high-sensitive methods in UV optical spectroscopy, non-line-of-sight communication, etc.

This situation is determined by a number of problems, starting with the high defectiveness of structures when they are grown on heterosubstrates due to the lack of economically reasonable bulk homosubstrates. The negative influence of defects in AlGaN nanoheterostructures is enhanced by the absence of pronounced effects of charge carrier localization, which have already played a key role in the revolutionary development of high-performance In-containing optoelectronics operating in the visible and UV-A spectral ranges.

This Special Issue will be devoted to the problems of increasing the efficiency of UV-C optoelectronic devices by proposing new ideas in the field of both epitaxial growth of (Al,Ga)N nanoheterostructures using various technologies and post-growth processing of structures. This activity was started in the previous Special Issue “Semiconductor Heterostructures with Quantum Wells, Quantum Dots and Superlattices”, and in this issue, we welcome new approaches to create (Al,Ga)N-based nanoheterostructures with an accuracy of several monolayers and controlled change in composition and elastic stresses. Special attention will be paid to the study of epitaxial growth modes of monolayer-thick (Al,Ga)N nanoheterostructures, charge carrier localization effects, and exciton nature of luminescence in such quantum-sized structures.

Dr. Valentin Jmerik
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

 

Keywords

  • AlGaN-based nanoheterostructures
  • UV-C optoelectronics
  • monolayer-thick quantum wells
  • nanorods
  • molecular beam epitaxy
  • metalorganic chemical vapor deposition
  • epitaxial growth mechanisms
  • exciton
  • localization of charge carriers

Published Papers (4 papers)

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Research

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13 pages, 4213 KiB  
Article
(Al, Ga)N-Based Quantum Dots Heterostructures on h-BN for UV-C Emission
by Aly Zaiter, Nikita Nikitskiy, Maud Nemoz, Phuong Vuong, Vishnu Ottapilakkal, Suresh Sundaram, Abdallah Ougazzaden and Julien Brault
Nanomaterials 2023, 13(17), 2404; https://doi.org/10.3390/nano13172404 - 24 Aug 2023
Viewed by 1026
Abstract
Aluminium Gallium Nitride (AlyGa1-yN) quantum dots (QDs) with thin sub-µm AlxGa1-xN layers (with x > y) were grown by molecular beam epitaxy on 3 nm and 6 nm thick hexagonal boron nitride (h-BN) initially deposited [...] Read more.
Aluminium Gallium Nitride (AlyGa1-yN) quantum dots (QDs) with thin sub-µm AlxGa1-xN layers (with x > y) were grown by molecular beam epitaxy on 3 nm and 6 nm thick hexagonal boron nitride (h-BN) initially deposited on c-sapphire substrates. An AlN layer was grown on h-BN and the surface roughness was investigated by atomic force microscopy for different deposited thicknesses. It was shown that for thicker AlN layers (i.e., 200 nm), the surface roughness can be reduced and hence a better surface morphology is obtained. Next, AlyGa1-yN QDs embedded in Al0.7Ga0.3N cladding layers were grown on the AlN and investigated by atomic force microscopy. Furthermore, X-ray diffraction measurements were conducted to assess the crystalline quality of the AlGaN/AlN layers and examine the impact of h-BN on the subsequent layers. Next, the QDs emission properties were studied by photoluminescence and an emission in the deep ultra-violet, i.e., in the 275–280 nm range was obtained at room temperature. Finally, temperature-dependent photoluminescence was performed. A limited decrease in the emission intensity of the QDs with increasing temperatures was observed as a result of the three-dimensional confinement of carriers in the QDs. Full article
(This article belongs to the Special Issue (Al, Ga)N-Based Nanostructures for UV-C Optoelectronics)
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14 pages, 2960 KiB  
Article
Single-Exciton Photoluminescence in a GaN Monolayer inside an AlN Nanocolumn
by Eugenii Evropeitsev, Dmitrii Nechaev, Valentin Jmerik, Yuriy Zadiranov, Marina Kulagina, Sergey Troshkov, Yulia Guseva, Daryia Berezina, Tatiana Shubina and Alexey Toropov
Nanomaterials 2023, 13(14), 2053; https://doi.org/10.3390/nano13142053 - 12 Jul 2023
Viewed by 856
Abstract
GaN/AlN heterostructures with thicknesses of one monolayer (ML) are currently considered to be the most promising material for creating UVC light-emitting devices. A unique functional property of these atomically thin quantum wells (QWs) is their ability to maintain stable excitons, resulting in a [...] Read more.
GaN/AlN heterostructures with thicknesses of one monolayer (ML) are currently considered to be the most promising material for creating UVC light-emitting devices. A unique functional property of these atomically thin quantum wells (QWs) is their ability to maintain stable excitons, resulting in a particularly high radiation yield at room temperature. However, the intrinsic properties of these excitons are substantially masked by the inhomogeneous broadening caused, in particular, by fluctuations in the QWs’ thicknesses. In this work, to reduce this effect, we fabricated cylindrical nanocolumns of 50 to 5000 nm in diameter using GaN/AlN single QW heterostructures grown via molecular beam epitaxy while using photolithography with a combination of wet and reactive ion etching. Photoluminescence measurements in an ultrasmall QW region enclosed in a nanocolumn revealed that narrow lines of individual excitons were localized on potential fluctuations attributed to 2-3-monolayer-high GaN clusters, which appear in QWs with an average thickness of 1 ML. The kinetics of luminescence with increasing temperature is determined via the change in the population of localized exciton states. At low temperatures, spin-forbidden dark excitons with lifetimes of ~40 ns predominate, while at temperatures elevated above 120 K, the overlying bright exciton states with much faster recombination dynamics determine the emission. Full article
(This article belongs to the Special Issue (Al, Ga)N-Based Nanostructures for UV-C Optoelectronics)
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24 pages, 14218 KiB  
Article
2D-GaN/AlN Multiple Quantum Disks/Quantum Well Heterostructures for High-Power Electron-Beam Pumped UVC Emitters
by Valentin Jmerik, Dmitrii Nechaev, Alexey Semenov, Eugenii Evropeitsev, Tatiana Shubina, Alexey Toropov, Maria Yagovkina, Prokhor Alekseev, Bogdan Borodin, Kseniya Orekhova, Vladimir Kozlovsky, Mikhail Zverev, Nikita Gamov, Tao Wang, Xinqiang Wang, Markus Pristovsek, Hiroshi Amano and Sergey Ivanov
Nanomaterials 2023, 13(6), 1077; https://doi.org/10.3390/nano13061077 - 16 Mar 2023
Cited by 2 | Viewed by 1495
Abstract
This article describes GaN/AlN heterostructures for ultraviolet-C (UVC) emitters with multiple (up to 400 periods) two-dimensional (2D)-quantum disk/quantum well structures with the same GaN nominal thicknesses of 1.5 and 16 ML-thick AlN barrier layers, which were grown by plasma-assisted molecular-beam epitaxy in a [...] Read more.
This article describes GaN/AlN heterostructures for ultraviolet-C (UVC) emitters with multiple (up to 400 periods) two-dimensional (2D)-quantum disk/quantum well structures with the same GaN nominal thicknesses of 1.5 and 16 ML-thick AlN barrier layers, which were grown by plasma-assisted molecular-beam epitaxy in a wide range of gallium and activated nitrogen flux ratios (Ga/N2*) on c-sapphire substrates. An increase in the Ga/N2* ratio from 1.1 to 2.2 made it possible to change the 2D-topography of the structures due to a transition from the mixed spiral and 2D-nucleation growth to a purely spiral growth. As a result, the emission energy (wavelength) could be varied from 5.21 eV (238 nm) to 4.68 eV (265 nm) owing to the correspondingly increased carrier localization energy. Using electron-beam pumping with a maximum pulse current of 2 A at an electron energy of 12.5 keV, a maximum output optical power of 50 W was achieved for the 265 nm structure, while the structure emitting at 238 nm demonstrated a power of 10 W. Full article
(This article belongs to the Special Issue (Al, Ga)N-Based Nanostructures for UV-C Optoelectronics)
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Review

Jump to: Research

19 pages, 1615 KiB  
Review
Towards Efficient Electrically-Driven Deep UVC Lasing: Challenges and Opportunities
by Sergey Nikishin, Ayrton Bernussi and Sergey Karpov
Nanomaterials 2023, 13(1), 185; https://doi.org/10.3390/nano13010185 - 31 Dec 2022
Cited by 1 | Viewed by 1915
Abstract
The major issues confronting the performance of deep-UV (DUV) laser diodes (LDs) are reviewed along with the different approaches aimed at performance improvement. The impact of threading dislocations on the laser threshold current, limitations on heavy n- and p-doping in Al-rich AlGaN alloys, [...] Read more.
The major issues confronting the performance of deep-UV (DUV) laser diodes (LDs) are reviewed along with the different approaches aimed at performance improvement. The impact of threading dislocations on the laser threshold current, limitations on heavy n- and p-doping in Al-rich AlGaN alloys, unavoidable electron leakage into the p-layers of (0001) LD structures, implementation of tunnel junctions, and non-uniform hole injection into multiple quantum wells in the active region are discussed. Special attention is paid to the current status of n- and p-type doping and threading dislocation density reduction, both being the factors largely determining the performance of DUV-LDs. It is shown that most of the above problems originate from intrinsic properties of the wide-bandgap AlGaN semiconductors, which emphasizes their fundamental role in the limitation of deep-UV LD performance. Among various remedies, novel promising technological and design approaches, such as high-temperature face-to-face annealing and distributed polarization doping, are discussed. Whenever possible, we provided a comparison between the growth capabilities of MOVPE and MBE techniques to fabricate DUV-LD structures. Full article
(This article belongs to the Special Issue (Al, Ga)N-Based Nanostructures for UV-C Optoelectronics)
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