Special Issue "Advances in GaN Crystals and Their Applications"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystal Engineering".

Deadline for manuscript submissions: closed (30 September 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Ikai Lo

Department of Physics, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University
Website | E-Mail
Interests: Molecular beam epitaxy (MBE); Metal–Organic Chemical Vapor Deposition (MOCVD); crystal characterization; GaN-based nanostructures/devices/applications

Special Issue Information

Dear Colleagues,

The wide bandgap, GaN, has been extensively investigated and applied in optoelectronic devices and high electron mobility transistors. The bandgap of (In,Al)GaN alloy compound covers the entire solar radiation spectrum from ultraviolet to infrared rays. Furthermore, the Stark effect induced by piezoelectric and the spontaneous electric field on polar GaN epi-film creates fundamental properties in optoelectronic applications. The nanostructure of GaN can be grown by advanced techniques, such as plasma-assisted molecular beam epitaxy, metal–organic chemical vapor deposition, etc. The nanostructured GaN opens a new area to optimize quantum properties in applications for high-efficient optoelectronic devices.

We invite investigators to contribute original articles on their current study of the GaN structure, growth technology, crystal properties, and their applications. Both experimental and theoretical papers are welcome.

Potential topics include without being limited to:

  • Theory, modelling of GaN-based thin films, nanostructures and heterostructures,

  • Fabrication, growth mechanism of GaN epilayers, bulk, heterostructure and nanostructure by MBE, MOCVE, HVPE, ALD, ....

  • Characterization of GaN epilayer, bulk, heterostructure and nanostructure by TEM, PL, CL, Raman, SIMS, XPS, ....

  • Application, processing of GaN-based devices, such as light-emitting diodes (LED), solar cells, laser diodes (LD), high electron mobility transistors (HEMT), detectors, ....

Prof. Dr. Ikai Lo
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 papers will be 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 1200 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

  • GaN

  • MBE

  • MOCVD

  • Light-emitting diodes

  • High electron mobility transistors

Published Papers (7 papers)

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Editorial

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Open AccessEditorial Advances in GaN Crystals and Their Applications
Crystals 2018, 8(3), 117; https://doi.org/10.3390/cryst8030117
Received: 27 February 2018 / Revised: 1 March 2018 / Accepted: 2 March 2018 / Published: 3 March 2018
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Abstract
This special issue looks at the potential applications of GaN-based crystals in both fields of nano-electronics and optoelectronics. The contents will focus on the fabrication and characterization of GaN-based thin films and nanostructures. It consists of six papers, indicating the current developments in
[...] Read more.
This special issue looks at the potential applications of GaN-based crystals in both fields of nano-electronics and optoelectronics. The contents will focus on the fabrication and characterization of GaN-based thin films and nanostructures. It consists of six papers, indicating the current developments in GaN-related technology for high-efficiency sustainable electronic and optoelectronic devices, which include the role of the AlN layer in high-quality AlGaN/GaN heterostructures for advanced high-mobility electronic applications and simulation of GaN-based nanorod high-efficiency light-emitting diodes for optoelectronic applications. From the results, one can learn the information and experience available in the advanced fabrication of nanostructured GaN-based crystals for nano-electronic and optoelectronic devices. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)

Research

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Open AccessArticle Evaluation of Light Extraction Efficiency of GaN-Based Nanorod Light-Emitting Diodes by Averaging over Source Positions and Polarizations
Crystals 2018, 8(1), 27; https://doi.org/10.3390/cryst8010027
Received: 15 December 2017 / Revised: 7 January 2018 / Accepted: 8 January 2018 / Published: 10 January 2018
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Abstract
Light extraction efficiency (LEE) of GaN-based nanorod blue light-emitting diode (LED) structures is investigated using finite-difference time-domain (FDTD) simulations. When the LEE is calculated for different source positions inside the nanorod, the LEE is found to depend strongly on the source positions and
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Light extraction efficiency (LEE) of GaN-based nanorod blue light-emitting diode (LED) structures is investigated using finite-difference time-domain (FDTD) simulations. When the LEE is calculated for different source positions inside the nanorod, the LEE is found to depend strongly on the source positions and the polarization directions for each source position, implying that the LEE of nanorod LED structures should be evaluated by averaging over source positions and polarization directions for determining the LEE accurately. The averaged LEE of nanorod LED structures is simulated as the radius, the p-GaN thickness, and the n-GaN thickness is varied, and the optimum structural parameters can be obtained. In addition, the far-field pattern is simulated when considering the averaging effects, and the circularly symmetric and uniform emission distribution is obtained. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)
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Open AccessArticle Simulation Model Development for Packaged Cascode Gallium Nitride Field-Effect Transistors
Crystals 2017, 7(8), 250; https://doi.org/10.3390/cryst7080250
Received: 24 June 2017 / Revised: 4 August 2017 / Accepted: 6 August 2017 / Published: 9 August 2017
Cited by 1 | PDF Full-text (5539 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a simple behavioral model with experimentally extracted parameters for packaged cascode gallium nitride (GaN) field-effect transistors (FETs). This study combined a level-1 metal–oxide–semiconductor field-effect transistor (MOSFET), a junction field-effect transistor (JFET), and a diode model to simulate a cascode GaN
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This paper presents a simple behavioral model with experimentally extracted parameters for packaged cascode gallium nitride (GaN) field-effect transistors (FETs). This study combined a level-1 metal–oxide–semiconductor field-effect transistor (MOSFET), a junction field-effect transistor (JFET), and a diode model to simulate a cascode GaN FET, in which a JFET was used to simulate a metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT). Using the JFET to simulate the MIS-HEMT not only ensures that the curve fits an S-shape transfer characteristic but also enables the pinch-off voltages extracted from the threshold voltage of the MIS-HEMT to be used as a watershed to distinguish where the drop in parasitic capacitance occurs. Parameter extraction was based on static and dynamic characteristics, which involved simulating the behavior of the created GaN FET model and comparing the extracted parameters with experimental measurements to demonstrate the accuracy of the simulation program with an integrated circuit emphasis (SPICE) model. Cascode capacitance was analyzed and verified through experimental measurements and SPICE simulations. The analysis revealed that the capacitance of low-voltage MOSFETs plays a critical role in increasing the overall capacitance of cascode GaN FETs. The turn-off resistance mechanism effectively described the leakage current, and a double-pulse tester was used to evaluate the switching performance of the fabricated cascode GaN FET. LTspice simulation software was adopted to compare the experimental switching results. Overall, the simulation results were strongly in agreement with the experimental results. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)
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Graphical abstract

Open AccessArticle AlGaN/GaN MOS-HEMTs with Corona-Discharge Plasma Treatment
Crystals 2017, 7(5), 146; https://doi.org/10.3390/cryst7050146
Received: 29 April 2017 / Revised: 13 May 2017 / Accepted: 16 May 2017 / Published: 18 May 2017
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Abstract
The effects of a corona-discharge plasma treatment on the performance of an AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor fabricated onto Si substrates were studied. The threshold voltage shifted from −8.15 to −4.21 V when the device was treated with an Al2O3
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The effects of a corona-discharge plasma treatment on the performance of an AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor fabricated onto Si substrates were studied. The threshold voltage shifted from −8.15 to −4.21 V when the device was treated with an Al2O3 layer. The leakage current was reduced from 2.9 × 10−5 to 4.2 × 10−7 mA/mm, and the ION/IOFF ratio increased from 8.3 × 106 to 7.3 × 108 using the corona-discharge plasma treatment, which exhibited an increase of about two orders of magnitude. The device exhibited excellent performance with a subthreshold swing of 78 mV/dec and a peak gain of 47.92 mS/mm at VGS = 10 V. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)
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Open AccessArticle On the Role of AlN Insertion Layer in Stress Control of GaN on 150-mm Si (111) Substrate
Crystals 2017, 7(5), 134; https://doi.org/10.3390/cryst7050134
Received: 12 April 2017 / Revised: 5 May 2017 / Accepted: 9 May 2017 / Published: 12 May 2017
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Abstract
In this study, low-temperature (LT) and high-temperature (HT) AlN insertion layers (ILs) grown at 680 and 970 °C were integrated with 3.7-μm GaN-based heterostructure grown on 150-mm Si (111) substrates by metalorganic chemical vapor deposition. Under a V/III flow ratio of 1960, the
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In this study, low-temperature (LT) and high-temperature (HT) AlN insertion layers (ILs) grown at 680 and 970 °C were integrated with 3.7-μm GaN-based heterostructure grown on 150-mm Si (111) substrates by metalorganic chemical vapor deposition. Under a V/III flow ratio of 1960, the GaN epilayer with a continuous interface resulting from the LT AlN IL was subject to a compressive stress of −0.109 GPa. However, the GaN epilayer with discontinuous interfaces resulting from the HT AlN IL growth under the same flow ratio was subject to a tensile stress of 0.174 GPa. To realize continuous interfaces between the GaN epilayer and HT AlN IL, a higher V/III ratio of 5960 was utilized to suppress the decomposition of GaN. It results in changing the stress state of the GaN-based heterostructure from tensile to compressive. This strategic finding indicates that a stress-controllable GaN on Si can be achieved via the incorporation of HT AlN ILs. A minimum curvature at 5 km−1 is demonstrated for the 3.7-μm GaN-based heterostructure on a 150-mm Si (111) substrate, which has high potential for power switching device applications. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)
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Open AccessArticle Effects of Al and N2 Flow Sequences on the Interface Formation of AlN on Sapphire by EVPE
Crystals 2017, 7(5), 123; https://doi.org/10.3390/cryst7050123
Received: 15 March 2017 / Revised: 18 April 2017 / Accepted: 21 April 2017 / Published: 27 April 2017
Cited by 1 | PDF Full-text (1182 KB) | HTML Full-text | XML Full-text
Abstract
The interface formation mechanisms of AlN films on sapphire substrates grown by the elementary source vapor phase epitaxy (EVPE) method, which is a new AlN bulk fabrication method using Al and N2 as precursors, are investigated. Supplying N2 after the substrate
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The interface formation mechanisms of AlN films on sapphire substrates grown by the elementary source vapor phase epitaxy (EVPE) method, which is a new AlN bulk fabrication method using Al and N2 as precursors, are investigated. Supplying N2 after the substrate temperature reaches the growth temperature [Process N2(GT)] causes the interface to become rough due to the thermal decomposition of sapphire. Self-separation occasionally occurs with the Process N2(GT), suggesting that the rough interface generates self-separating films with little strain. On the other hand, supplying N2 beginning at room temperature forms a relatively smooth interface with voids, which can be realized by the reaction between a nitrided sapphire surface and an Al source. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)
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Review

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Open AccessReview Status of Growth of Group III-Nitride Heterostructures for Deep Ultraviolet Light-Emitting Diodes
Crystals 2017, 7(10), 300; https://doi.org/10.3390/cryst7100300
Received: 4 September 2017 / Revised: 28 September 2017 / Accepted: 29 September 2017 / Published: 4 October 2017
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Abstract
We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV) light-emitting diodes (LEDs), with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current
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We overview recent progress in growth aspects of group III-nitride heterostructures for deep ultraviolet (DUV) light-emitting diodes (LEDs), with particular emphasis on the growth approaches for attaining high-quality AlN and high Al-molar fraction AlGaN. The discussion commences with the introduction of the current status of group III-nitride DUV LEDs and the remaining challenges. This segues into discussion of LED designs enabling high device performance followed by the review of advances in the methods for the growth of bulk single crystal AlN intended as a native substrate together with a discussion of its UV transparency. It should be stated, however, that due to the high-cost of bulk AlN substrates at the time of writing, the growth of DUV LEDs on foreign substrates such as sapphire still dominates the field. On the deposition front, the heteroepitaxial growth approaches incorporate high-temperature metal organic chemical vapor deposition (MOCVD) and pulsed-flow growth, a variant of MOCVD, with the overarching goal of enhancing adatom surface mobility, and thus epitaxial lateral overgrowth which culminates in minimization the effect of lattice- and thermal-mismatches. This is followed by addressing the benefits of pseudomorphic growth of strained high Al-molar fraction AlGaN on AlN. Finally, methods utilized to enhance both p- and n-type conductivity of high Al-molar fraction AlGaN are reviewed. Full article
(This article belongs to the Special Issue Advances in GaN Crystals and Their Applications)
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