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In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution...
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In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution to Blue Light-emitting Diodes

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Materials for Energy Applications".

Deadline for manuscript submissions: closed (1 October 2023) | Viewed by 14384

Special Issue Editor

Dr. Paul J. Simmonds

E-Mail Website
Guest Editor
Quantum Nanomaterials Laboratory, Electrical and Computer Engineering, Tufts University, Medford, MA 02155, USA
Interests: molecular beam epitaxy; III-V semiconductors; self-assembled nanostructures; quantum dots; tensile strain; epitaxial 2D materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to Professor Shuji Nakamura in recognition of the 30th anniversary of his invention of the blue light emitting diode (LED) based on GaN. His invention was the catalyst for rapid developments in multiple fields, from solid-state lighting to advanced display technologies. Professor Nakamura has received many accolades and awards for his pioneering research into III-nitride materials and devices, including the 2014 Nobel Prize in Physics.

This Special Issue is an opportunity for the international academic and industry research communities to share their latest experimental and theoretical discoveries in the synthesis and applications of III-nitride semiconductors. We are also interested in discussions regarding key challenges and future directions for this critical research field that was first opened up by the work of Prof. Nakamura.

Dr. Paul J. Simmonds
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. Crystals is an international peer-reviewed open access monthly 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 2100 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

  • gallium nitride
  • GaN
  • nitride semiconductors
  • III-N
  • blue LED
  • InN
  • AlN
  • dilute nitride

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Published Papers (5 papers)

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Research

11 pages, 3468 KiB  
Article
Interferometric Optical Pumping of an InGaN/GaN-Based Gain-Coupled Distributed Feedback Multi Quantum Well Laser
by Daniel Hofstetter, Hans Beck and David P. Bour
Crystals 2023, 13(12), 1689; https://doi.org/10.3390/cryst13121689 - 15 Dec 2023
Viewed by 1594
Abstract
We describe an all-optical method to achieve—prior to further advanced processing steps—a perfect match of the relevant wavelength-sensitive parameters of an InGaN/GaN semiconductor distributed feedback laser. Instead of permanently etching and epitaxially over-growing a waveguide-based diffraction grating for the definition of an index-coupled [...] Read more.
We describe an all-optical method to achieve—prior to further advanced processing steps—a perfect match of the relevant wavelength-sensitive parameters of an InGaN/GaN semiconductor distributed feedback laser. Instead of permanently etching and epitaxially over-growing a waveguide-based diffraction grating for the definition of an index-coupled distributed feedback laser, we suggest here—by employing a powerful ultraviolet pump laser—a non-permanent, photoinduced generation of an optical diffraction grating. The resulting complex refractive index modulation then forms a gain-coupled distributed feedback laser. Such an approach has the advantage of remaining flexible as long as possible—both in terms of the correct grating period and the ideal coupling constant. This flexibility is maintained until the definitive etch and the epitaxial over-growth of the diffraction grating are completed. Such devices can—like their dye laser counterparts in the early seventies—also be used as ultra-broadly tunable single-mode sources. Full article
(This article belongs to the Special Issue In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution to Blue Light-emitting Diodes)
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14 pages, 580 KiB  
Article
Many-Body Calculations of Excitons in Two-Dimensional GaN
by Yachao Zhang
Crystals 2023, 13(7), 1048; https://doi.org/10.3390/cryst13071048 - 1 Jul 2023
Cited by 2 | Viewed by 2990
Abstract
We present an ab initio study on quasiparticle (QP) excitations and excitonic effects in two-dimensional (2D) GaN based on density-functional theory and many-body perturbation theory. We calculate the QP band structure using GW approximation, which generates an indirect band gap of 4.83 [...] Read more.
We present an ab initio study on quasiparticle (QP) excitations and excitonic effects in two-dimensional (2D) GaN based on density-functional theory and many-body perturbation theory. We calculate the QP band structure using GW approximation, which generates an indirect band gap of 4.83 eV (K→Γ) for 2D GaN, opening up 1.24 eV with respect to its bulk counterpart. It is shown that the success of plasmon-pole approximation in treating the 2D material benefits considerably from error cancellation. On the other hand, much better gaps, comparable to GW ones, could be obtained by correcting the Kohn–Sham gap with a derivative discontinuity of the exchange–correlation functional at much lower computational cost. To evaluate excitonic effects, we solve the Bethe–Salpeter equation (BSE) starting from Kohn–Sham eigenvalues with a scissors operator to open the single-particle gap. This approach yields an exciton binding energy of 1.23 eV in 2D GaN, which is in good agreement with the highly demanding GW-BSE results. The enhanced excitonic effects due to reduced dimensionality are discussed by comparing the optical spectra from BSE calculations with that by random-phase approximation (RPA) for both the monolayer and bulk GaN in wurtzite phase. Additionally, we find that the spin–orbit splitting of excitonic peaks is noticeable in 2D GaN but buried in the bulk crystal. Full article
(This article belongs to the Special Issue In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution to Blue Light-emitting Diodes)
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9 pages, 1888 KiB  
Article
Two-Step GaN Layer Growth for High-Voltage Lateral AlGaN/GaN HEMT
by Yusnizam Yusuf, Muhammad Esmed Alif Samsudin, Muhamad Ikram Md Taib, Mohd Anas Ahmad, Mohamed Fauzi Packeer Mohamed, Hiroshi Kawarada, Shaili Falina, Norzaini Zainal and Mohd Syamsul
Crystals 2023, 13(1), 90; https://doi.org/10.3390/cryst13010090 - 3 Jan 2023
Cited by 8 | Viewed by 3467
Abstract
This paper presents reduced dislocation of the AlGaN/GaN heterostructure for high-voltage lateral high-electron-mobility transistor (HEMT) devices. AlGaN/GaN heterostructure was grown on sapphire substrate. Prior to the growth of the AlGaN layer, the GaN layer was grown via two-step growth. In the first step, [...] Read more.
This paper presents reduced dislocation of the AlGaN/GaN heterostructure for high-voltage lateral high-electron-mobility transistor (HEMT) devices. AlGaN/GaN heterostructure was grown on sapphire substrate. Prior to the growth of the AlGaN layer, the GaN layer was grown via two-step growth. In the first step, the V/III ratio was applied at 1902 and then at 3046 in the second step. The FWHMs of the XRD (002) and (102) peaks of the GaN layer were around 205 arcsec ((002) peak) and 277 arcsec ((102) peak). Moreover, the surface of the GaN layer showed clear evidence of step flows, which resulted in the smooth surface of the layer as well as the overgrown of the AlGaN layer. Subsequently, the AlGaN/GaN heterostructure was fabricated into a lateral HEMT with wide gate-to-drain length (LGD). The device exhibited a clear working HEMT characteristic with high breakdown voltages up to 497 V. In comparison to many reported AlGaN/GaN HEMTs, no AlGaN interlayer was inserted in our AlGaN/GaN heterostructure. By improving the growth conditions for the two-step growth, the performance of AlGaN/GaN HEMTs could be improved further. Full article
(This article belongs to the Special Issue In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution to Blue Light-emitting Diodes)
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7 pages, 1485 KiB  
Article
Performance Improvement of InGaN-Based LEDs via a Current-Blocking Region Prepared via Hydrogen Passivation
by Pavel Kirilenko, Cesur Altinkaya, Daisuke Iida and Kazuhiro Ohkawa
Crystals 2022, 12(12), 1733; https://doi.org/10.3390/cryst12121733 - 1 Dec 2022
Cited by 2 | Viewed by 1938
Abstract
We report p-GaN passivation via hydrogen plasma used to create current blocking regions (CBRs) in InGaN-based green LEDs with standard dimensions of 280 × 650 μm2. The CBRs are created before mesa etching in two variants: underneath the opaque metal p-pad [...] Read more.
We report p-GaN passivation via hydrogen plasma used to create current blocking regions (CBRs) in InGaN-based green LEDs with standard dimensions of 280 × 650 μm2. The CBRs are created before mesa etching in two variants: underneath the opaque metal p-pad and both underneath the p-pad and along the device’s mesa perimeter. The peak EQE increased by 13% and 23% in the first and the second cases, respectively, in comparison to the reference LED with no CBR. With a high injection current of 50 A/cm2, the EQE value increased by 2% in the case of CBRs underneath the p-pad as well as by 14% in the case of CBRs both underneath the p-pad and along the mesa perimeter (relative to the reference sample with no CBR). Full article
(This article belongs to the Special Issue In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution to Blue Light-emitting Diodes)
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9 pages, 2683 KiB  
Article
Fully Relaxed, Crack-Free AlGaN with upto 50% Al Composition Grown on Porous GaN Pseudo-Substrate
by Nirupam Hatui, Henry Collins, Emmanuel Kayede, Shubhra S. Pasayat, Weiyi Li, Stacia Keller and Umesh K. Mishra
Crystals 2022, 12(7), 989; https://doi.org/10.3390/cryst12070989 - 16 Jul 2022
Cited by 3 | Viewed by 2997
Abstract
Fully relaxed, crack free, smooth AlxGa1−xN layers with up to 50% Al composition were demonstrated on pseudo-substrates composed of dense arrays of 10 × 10 µm2 compliant porous GaN-on-porous-GaN tiles. The AlGaN layers were grown in steps for [...] Read more.
Fully relaxed, crack free, smooth AlxGa1−xN layers with up to 50% Al composition were demonstrated on pseudo-substrates composed of dense arrays of 10 × 10 µm2 compliant porous GaN-on-porous-GaN tiles. The AlGaN layers were grown in steps for a total of 1.3 µm. The growth conditions necessary to demonstrate high quality films at higher Al compositions also suppressed any sidewall growth. Full article
(This article belongs to the Special Issue In Celebration of the 30th Anniversary of Shuji Nakamura’s Contribution to Blue Light-emitting Diodes)
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