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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 (31 May 2023) | Viewed by 29880

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Special Issue Editors

Dr. Mingsheng Xu

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Guest Editor

Institute of Novel Semiconductors, Shandong University, Jinan 250100, China
Interests: silicon carbide power devices; gallium nitride epitaxial growth; diamond devices; gallium oxide materials and devices

Dr. Qiang Li

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Guest Editor

Department of Electronics, School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Interests: III-V semiconductor; deep ultraviolet LED; boron nitride materials and devices; UV detector

Dr. Giuseppe Greco

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CNR-IMM, Institute for Microelectronics and Microsystems, Zona Industriale Strada VIII No. 5, 95121 Catania, Italy
Interests: wide band gap semiconductors; III-V heterostructures; metal-semiconductors interface

Dr. Vladimir M. Kaganer

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Guest Editor

Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
Interests: theories of x-ray diffraction and crystal growth; x-ray diffraction from crystal lattice defects; III-V nanowires for optoelectronics

Special Issue Information

Dear Colleagues,

Wide-bandgap semiconductor materials have unique electrical, optical, and magnetic properties. Their devices have excellent performance and broad application prospects in many fields, which can improve the working temperature limit of power devices and make them work in worse environments; improve the power and efficiency of devices and, consequently, the performance of equipment; and broaden the luminous spectrum and realize full-color displays. With the gradual maturation of material growth and device preparation technology, wide-band semiconductor materials and devices already hold overwhelming superiority in the electronic information industry. The development of wide-bandgap semiconductors, however, does not only offer opportunities but also faces great challenges. With the increasing requirements of optoelectronic devices, power devices, and microwave devices for high frequency, high speed, high temperature, and high power, it is urgent to develop and improve the existing materials and seek new ones. We know that 3rd-generation semiconductor materials are mainly wide-bandgap semiconductors represented by GaN and SiC. Ultrawide-bandgap semiconductor materials include AlN, Ga₂O₃, diamond, BN, and so on. The introduction of these new materials represents a significant development and supplements semiconductor systems. At this stage, the growth, fabrication, and characterization of wide-bandgap semiconductor materials and devices need to be strengthened and improved. It is also necessary to systematically summarize recent works so that researchers in this field can learn from each other and jointly promote the development of wide-bandgap semiconductor materials and devices.

Dr. Mingsheng Xu
Dr. Qiang Li
Dr. Giuseppe Greco
Dr. Vladimir M. Kaganer
Guest Editors

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Keywords

III-V semiconductors (GaN, etc.)
SiC materials and devices
AlN crystals and templates
BN growth and fundamental properties
heterostructure physics
first-principles calculation
deep UV–LEDs
photodetectors
nanostructures and nanodevices
diamonds materials and devices
gallium oxide materials and devices
green and blue laser diodes

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Published Papers (10 papers)

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Research

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13 pages, 5140 KiB

Open AccessArticle

Study of Magnesium Activation Effect on Pinch-Off Voltage of Normally-Off p-GaN HEMTs for Power Applications

by Giovanni Giorgino, Giuseppe Greco, Maurizio Moschetti, Cristina Miccoli, Maria Eloisa Castagna, Cristina Tringali, Patrick Fiorenza, Fabrizio Roccaforte and Ferdinando Iucolano

Crystals 2023, 13(9), 1309; https://doi.org/10.3390/cryst13091309 - 27 Aug 2023

Viewed by 2609

Abstract

The role of the magnesium (Mg) doping and its electrical activation on the off-state of p-GaN/AlGaN/GaN HEMTs has been investigated in this work. Firstly, the effect of different Mg doping profiles has been studied via the help of Technology Computer-Aided Design (TCAD) simulations, with the objective of analyzing the band diagrams of the structure. Then, it has been shown how experimental Capacitance–Voltage measurements can be useful to obtain information on the net acceptor concentration in the p-GaN. As a result, devices with an undoped (magnesium-free) GaN gate have been experimentally compared to devices whose p-GaN gate has been activated via a reference annealing process. Finally, results on a device characterized by an improved p-GaN activation have been presented and compared, showing improvements on several parameters of both off- and on-state, thus underlining the key role of the Mg activation process in the overall performances of normally-off GaN HEMTs. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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14 pages, 2148 KiB

Open AccessArticle

Growth of N-Polar (000

\bar{1}

) GaN in Metal–Organic Vapour Phase Epitaxy on Sapphire

by Markus Pristovsek, Itsuki Furuhashi and Pietro Pampili

Crystals 2023, 13(7), 1072; https://doi.org/10.3390/cryst13071072 - 7 Jul 2023

Cited by 4 | Viewed by 1421

Abstract

We have systematically studied the growth of N-polar GaN on sapphire in metal–organic vapor phase epitaxy (MOVPE) on different misoriented (0001) sapphire substrates. The key parameter was the NH

_{3}

flow, which affects the roughness, growth rate, crystal quality, and impurities. Most parameters [...] Read more.

We have systematically studied the growth of N-polar GaN on sapphire in metal–organic vapor phase epitaxy (MOVPE) on different misoriented (0001) sapphire substrates. The key parameter was the NH

_{3}

flow, which affects the roughness, growth rate, crystal quality, and impurities. Most parameters show a trend reversal at a V/III ratio around 500 and show either a maximum, such as the growth rate, the sizes of hexagonal hillocks on low misorientations, the yellow luminescence and the mobility, or show a minimum such as the FWHM in X-ray diffraction, the carrier concentration, the surface roughness of large misorientations, or the blue (430 nm) luminescence. This suggests that around a V/III ratio of 500, the surface changes from a Ga-terminated Ga-adlayer surface to a N-terminated 3N-H

(2 \times 2)

surface. Using extremely low V/III ratios, a smooth N-polar GaN was obtained even on the standard 0.2° misorientation. However, good crystalline quality, low oxygen impurities and smooth surfaces together seem too challenging with low misorientation. The strain-dependent band edge shifted by 14 eV for strain along [000

\bar{1}

], which is close to the values reported by Ga-polar GaN. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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11 pages, 3960 KiB

Open AccessArticle

Effect of the Growth Interruption on the Surface Morphology and Crystalline Quality of MOCVD-Grown h-BN

by Qi Zhang, Yanan Guo, Zhibin Liu, Dadi Wang, Qiang Li, Jianchang Yan, Jinmin Li and Junxi Wang

Crystals 2023, 13(3), 486; https://doi.org/10.3390/cryst13030486 - 11 Mar 2023

Cited by 5 | Viewed by 2127

Abstract

Hexagonal boron nitride (h-BN) is one promising material class for applications in DUV optoelectronics due to the layered structure and ultra-wide bandgap. The synthesis of h-BN with smooth surface morphology and high quality on dielectric substrates is the key to construct efficient functional devices thereon. In this study, we reported wafer-scale h-BN on c-plane sapphire substrates by metal organic chemical vapor deposition utilizing the flow modulation epitaxy (FME) with growth interruptions. The effect of the growth interruption location within FME on the surface morphology and crystalline quality of h-BN films was systematically investigated. The interruption after the TEB injection could promote the mobility of B adatoms, and the interruption after the NH₃ injection could further relieve the passivation of N terminal growth fronts and mitigate the parasitic gas-phase reaction between growth precursors. By simultaneously employing interruptions after TEB and NH₃ injections, the growth rate of h-BN increased significantly from 0.16 nm/min to 4.76 nm/min, and the surface roughness of 2-nm-thick h-BN was reduced to 0.587 nm. In addition, h-BN grown with an interruption solely after the NH₃ injection presented the best crystallinity because the relatively slow growth rate reduced the possibility of impurity incorporation. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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9 pages, 3303 KiB

Open AccessEditor’s ChoiceArticle

Improved Electrical Performance of InAlN/GaN High Electron Mobility Transistors with Post Bis(trifluoromethane) Sulfonamide Treatment

by Siheng Chen, Peng Cui, Mingsheng Xu, Zhaojun Lin, Xiangang Xu, Yuping Zeng and Jisheng Han

Crystals 2022, 12(11), 1521; https://doi.org/10.3390/cryst12111521 - 26 Oct 2022

Viewed by 2221

Abstract

An enhancement of the electrical performance of the InAlN/GaN high electron mobility transistors (HEMTs) is demonstrated by the incorporation of post bis(trifluoromethane) sulfonamide (TFSI) treatment. The surface treatment of TFSI solution results in the increase of 2DEG electron mobility from 1180 to 1500 cm²/Vs and thus a reduction of on-state resistance and an increase in transconductance. The results indicate that the positive charge of H⁺ will decrease the polarization charges of the InAlN barrier under the access region due to the converse piezoelectric effect, leading to the reduced polarization Coulomb field (PCF) scattering in InAlN/GaN HEMT. This offers a possible way to improve the electron mobility and device performance of InAlN/GaN HEMTs for further application. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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8 pages, 3288 KiB

Open AccessArticle

Enhancement Mode Ga₂O₃ Field Effect Transistor with Local Thinning Channel Layer

by Lei Ge, Qiu Chen, Shuai Wang, Wenxiang Mu, Qian Xin, Zhitai Jia, Mingsheng Xu, Xutang Tao and Aimin Song

Crystals 2022, 12(7), 897; https://doi.org/10.3390/cryst12070897 - 24 Jun 2022

Cited by 3 | Viewed by 2502

Abstract

β−Ga₂O₃ field−effect transistors (FETs) were fabricated with and without local thinning to change the threshold voltage. A 220 nm Ga₂O₃ layer was mechanically exfoliated from a Cr−doped gallium oxide single crystal. Approximately 45 nm Ga₂O₃ was etched by inductively coupled plasma to form the local thinning. The threshold voltage of the device with etched local thinning increased from −3 V to +7 V compared to the unetched device. The effect of the local thinning was analyzed by device simulation, confirming that the local thinning structure is an effective method to enable enhancement−mode Ga₂O₃ FETs. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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6 pages, 3509 KiB

Open AccessArticle

Wafer−Scale Growth of Fe−Doped Hexagonal Boron Nitride (hBN) Films via Co−Sputtering

by Qiang Li, Qifan Zhang, Ransheng Chen, Haoran Zhang, Mingdi Wang, Jingping Zhu, Xiaoliang Wang, Yuhuai Liu and Feng Yun

Crystals 2022, 12(6), 777; https://doi.org/10.3390/cryst12060777 - 27 May 2022

Viewed by 2744

Abstract

Fe−doped hBN film has great potential for use in spintronic applications. The wafer scale preparation of Fe−doped hBN films and their material properties are crucial for application in devices. In this work, Fe−doped films with 2−inch wafer scale were fabricated by magnetron co−sputtering, and the properties of the films were characterized. The crystal quality decreased, but the electrical performance was greatly improved. The average square resistance of Fe−doped film was 0.34 KΩ/sqr. Meanwhile, the Fe−doped films kept the characteristics of hBN well. The wavelength of absorption edge was 216 nm, and the corresponding optical band gap of 5.76 eV. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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Review

Jump to: Research, Other

11 pages, 2516 KiB

Open AccessReview

Fabrication of Ohmic Contact on N-Type SiC by Laser Annealed Process: A Review

by Guo Li, Mingsheng Xu, Dongyang Zou, Yingxin Cui, Yu Zhong, Peng Cui, Kuan Yew Cheong, Jinbao Xia, Hongkun Nie, Shuqiang Li, Handoko Linewih, Baitao Zhang, Xiangang Xu and Jisheng Han

Crystals 2023, 13(7), 1106; https://doi.org/10.3390/cryst13071106 - 16 Jul 2023

Cited by 7 | Viewed by 4999

Abstract

In recent years, because of stringent needs in the fabrication of silicon carbide (SiC) power devices, laser annealing has been introduced to achieve local ohmic contact. In this paper, the laser annealing research for the ohmic contact process of SiC power devices is reviewed, which is mainly divided into four aspects: laser process mechanism, ohmic contact electrode materials, and substrate materials. The effect of laser parameters on ohmic contact and the annealing process on SiC diode devices is also reviewed. Progress of other substrate materials, namely 6H-SiC and semi-insulating 4H-SiC-based devices with laser annealed ohmic contacts, is also briefly discussed, in which formation of semi-insulating SiC ohmic contacts is derived from laser irradiation at the interface to produce 3C-SiC. Some experiment results have been shown in the passage, such as XRD, SEM, TEM, etc. In the review, it points out that the direction of application and development of the laser annealing process for improving the ohmic contact of SiC power devices is highly encouraging. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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40 pages, 13678 KiB

Open AccessReview

Deep Ultraviolet Photodetector: Materials and Devices

by Wannian Fang, Qiang Li, Jiaxing Li, Yuxuan Li, Qifan Zhang, Ransheng Chen, Mingdi Wang, Feng Yun and Tao Wang

Crystals 2023, 13(6), 915; https://doi.org/10.3390/cryst13060915 - 5 Jun 2023

Cited by 10 | Viewed by 4250

Abstract

The application of deep ultraviolet detection (DUV) in military and civil fields has increasingly attracted the attention of researchers’ attention. Compared with the disadvantages of organic materials, such as complex molecular structure and poor stability, inorganic materials are widely used in the field of DUV detection because of their good stability, controllable growth, and other characteristics. Rapid advances in preparing high-quality ultrawide-bandgap (UWBG) semiconductors have enabled the realization of various high-performance DUV photodetectors with different geometries, which provide an avenue for circumventing numerous disadvantages in traditional detectors. Herein, the development history and types of DUV detectors are briefly introduced. Typical UWBG detection materials and their preparation methods, as well as their research and application status in the field of DUV detection, are emphatically summarized and reviewed, including III-nitride semiconductors, gallium oxide, diamond, etc. Finally, problems pertaining to DUV detection materials, such as the growth of materials, the performance of devices, and their future development, are also discussed. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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25 pages, 5377 KiB

Open AccessReview

Research Progress in Capping Diamond Growth on GaN HEMT: A Review

by Yingnan Wang, Xiufei Hu, Lei Ge, Zonghao Liu, Mingsheng Xu, Yan Peng, Bin Li, Yiqiu Yang, Shuqiang Li, Xuejian Xie, Xiwei Wang, Xiangang Xu and Xiaobo Hu

Crystals 2023, 13(3), 500; https://doi.org/10.3390/cryst13030500 - 14 Mar 2023

Cited by 3 | Viewed by 3353

Abstract

With the increased power density of gallium nitride (GaN) high electron mobility transistors (HEMTs), effective cooling is required to eliminate the self-heating effect. Incorporating diamond into GaN HEMT is an alternative way to dissipate the heat generated from the active region. In this review, the four main approaches for the integration of diamond and GaN are briefly reviewed, including bonding the GaN wafer and diamond wafer together, depositing diamond as a heat-dissipation layer on the GaN epitaxial layer or HEMTs, and the epitaxial growth of GaN on the diamond substrate. Due to the large lattice mismatch and thermal mismatch, as well as the crystal structure differences between diamond and GaN, all above works face some problems and challenges. Moreover, the review is focused on the state-of-art of polycrystalline or nanocrystalline diamond (NCD) passivation layers on the topside of GaN HEMTs, including the nucleation and growth of the diamond on GaN HEMTs, structure and interface analysis, and thermal characterization, as well as electrical performance of GaN HEMTs after diamond film growth. Upon comparing three different nucleation methods of diamond on GaN, electrostatic seeding is the most commonly used pretreatment method to enhance the nucleation density. NCDs are usually grown at lower temperatures (600–800 °C) on GaN HEMTs, and the methods of “gate after growth” and selective area growth are emphasized. The influence of interface quality on the heat dissipation of capped diamond on GaN is analyzed. We consider that effectively reducing the thermal boundary resistance, improving the regional quality at the interface, and optimizing the stress–strain state are needed to improve the heat-spreading performance and stability of GaN HEMTs. NCD-capped GaN HEMTs exhibit more than a 20% lower operating temperature, and the current density is also improved, which shows good application potential. Furthermore, the existing problems and challenges have also been discussed. The nucleation and growth characteristics of diamond itself and the integration of diamond and GaN HEMT are discussed together, which can more completely explain the thermal diffusion effect of diamond for GaN HEMT and the corresponding technical problems. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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Other

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9 pages, 2097 KiB

Open AccessBrief Report

Hydrogen-Terminated Single Crystal Diamond MOSFET with a Bilayer Dielectric of Gd₂O₃/Al₂O₃

by Xiaoyong Lv, Wei Wang, Yanfeng Wang, Genqiang Chen, Shi He, Minghui Zhang and Hongxing Wang

Crystals 2023, 13(5), 783; https://doi.org/10.3390/cryst13050783 - 8 May 2023

Cited by 3 | Viewed by 1737

Abstract

In this paper, two dielectric layers of Al₂O₃ and Gd₂O₃ were prepared by an atomic layer deposition (ALD) and magnetron sputtering deposition (SD), respectively. Based on this, a metal-oxide-semiconductor field-effect transistor (MOSFET) was successfully prepared on a hydrogen-terminated single-crystal diamond (H-diamond), and its related properties were studied. The results showed that this device had typical p-type channel MOSFET output and transfer characteristics. In addition, the maximum current was 15.3 mA/mm, and the dielectric constant of Gd₂O₃ was 24.8. The effective mobility of MOSFET with Gd₂O₃/Al₂O₃ was evaluated to be 182.1 cm²/Vs. To the best of our knowledge, the bilayer dielectric of Gd₂O₃/Al₂O₃ was first used in a hydrogen-terminated diamond MOSFET and had the potential for application. Full article

(This article belongs to the Special Issue Wide-Bandgap Semiconductors)

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