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

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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 6385

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Dr. Paul J. Simmonds

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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
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Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to Professor Shuji Nakamura in recognition of the 30^th 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

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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 2600 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

Published Papers (4 papers)

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14 pages, 580 KiB

Open AccessArticle

Many-Body Calculations of Excitons in Two-Dimensional GaN

Yachao Zhang

Crystals 2023, 13(7), 1048; https://doi.org/10.3390/cryst13071048 - 01 Jul 2023

Viewed by 970

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

G W

approximation, which generates an indirect band gap of

4.83

[...] Read more.

G W

approximation, which generates an indirect band gap of

4.83

eV (

K \to 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

G W

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

G W

-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

Open AccessArticle

Two-Step GaN Layer Growth for High-Voltage Lateral AlGaN/GaN HEMT

Yusnizam Yusuf

Muhammad Esmed Alif Samsudin

Muhamad Ikram Md Taib

Mohd Anas Ahmad

Mohamed Fauzi Packeer Mohamed

and

Crystals 2023, 13(1), 90; https://doi.org/10.3390/cryst13010090 - 03 Jan 2023

Cited by 2 | Viewed by 1626

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, 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 (L_GD). 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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Figure 1

7 pages, 1485 KiB

Open AccessArticle

Performance Improvement of InGaN-Based LEDs via a Current-Blocking Region Prepared via Hydrogen Passivation

and

Crystals 2022, 12(12), 1733; https://doi.org/10.3390/cryst12121733 - 01 Dec 2022

Viewed by 1108

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 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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Figure 1

9 pages, 2683 KiB

Open AccessEditor’s ChoiceArticle

Fully Relaxed, Crack-Free AlGaN with upto 50% Al Composition Grown on Porous GaN Pseudo-Substrate

and

Crystals 2022, 12(7), 989; https://doi.org/10.3390/cryst12070989 - 16 Jul 2022

Viewed by 1855

Abstract

Fully relaxed, crack free, smooth Al_xGa_1−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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