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Crystals
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Semiconductor Nanocrystals
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Semiconductor Nanocrystals

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 19883

Special Issue Editors

Dr. Wei Xu

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Guest Editor
Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510641, China
Interests: photoelectric devices; flat panel display technology; microelectronics; printing electronics
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Honglong Ning

E-Mail Website
Guest Editor
Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510641, China
Interests: display system integrated engineering and technology
Dr. Hua Zheng

E-Mail Website
Guest Editor
School of Electrical Engineering and Intelligentization, Dongguan University of Technology, Dongguan, Guangdong 523808, China
Interests: semiconductor nanocrystals

Special Issue Information

Dear Colleagues,

Semiconductor nanocrystals have unique physical and chemical properties due to the size effect (excellent spectral properties, photochemical stability, carrier transport characteristics etc.) which are different from conventional semiconductor materials. After decades of research and development, semiconductor nanocrystals with various morphologies have been prepared, including semiconductor nanodot materials, semiconductor nanoribbon materials, semiconductor nanolinear materials, semiconductor nanotube materials, semiconductor nanothin layer materials, etc. In the field of photoelectric devices, quantum dot LEDs are an outstanding candidate for the next generation of new devices. In the field of solar cells, semiconductor nanocrystalline solar cells have the characteristics of low cost and long life, lending them excellent commercial potential. In chemical research, semiconductor nanocrystals have great development space because of their large specific surface area and high surface activity. In addition, semiconductor nanocrystals have shown a very broad application prospect in biological and medical fields. Therefore, the study of the fine control of the size, structure and surface of semiconductor nanocrystals is of great significance to the development and application of semiconductor nanocrystals.

As a whole, the Special Issue aims to summarize the basic knowledge and point out the challenges associated with semiconductor nanocrystals.

Dr. Wei Xu
Prof. Dr. Honglong Ning
Dr. Hua Zheng
Guest Editors

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

  • semiconductor nanocrystals
  • size effect
  • photoelectric devices
  • quantum dot

Published Papers (6 papers)

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Research

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10 pages, 26367 KiB  
Article
Cathodoluminescence of Ultrathin InAs Layers Embedded in GaAs Matrix
by Qigeng Yan, Siyuan Wang, Xiaojin Guan, Lei He, Kesheng Sun and Baolai Liang
Crystals 2022, 12(9), 1225; https://doi.org/10.3390/cryst12091225 - 31 Aug 2022
Cited by 8 | Viewed by 1332
Abstract
Ultrathin InAs layers with different thicknesses, from 0.75 to 1.4 monolayer, are grown in the GaAs matrix by molecular beam epitaxy on GaAs (001) substrates. For sub-monolayer heterostructures, islands or segregations exist during the growth process. Taking advantage of the high spatial resolution [...] Read more.
Ultrathin InAs layers with different thicknesses, from 0.75 to 1.4 monolayer, are grown in the GaAs matrix by molecular beam epitaxy on GaAs (001) substrates. For sub-monolayer heterostructures, islands or segregations exist during the growth process. Taking advantage of the high spatial resolution of focused electron beams, cathodoluminescence measurements obtain a smaller excitation spot than conventional photoluminescence. Based on the change on the peak position, line width, and intensity, cathodoluminescence spectra indicate that the size, geometry, and roughness develop with the InAs content. Moreover, spatial discontinuities of ultrathin InAs layers are observed on spectrum images and transmission electron microscopy images. This research reveals the correlation between the optical and structural properties of ultrathin InAs layers. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
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7 pages, 905 KiB  
Article
A Fast Recovery Vertical Superjunction MOSFET with n-Si and p-3C-SiC Pillars
by Rongyu Gao, Hongyu Cheng, Wenmao Li, Chenkai Deng, Jianguo Chen, Qing Wang and Hongyu Yu
Crystals 2022, 12(7), 916; https://doi.org/10.3390/cryst12070916 - 28 Jun 2022
Cited by 2 | Viewed by 1648
Abstract
In the traditional SJ MOSFET structure, n/p pillars with the same doping concentrations in the drift region are introduced to decrease the on-resistance. However, SJ MOSFET will turn on the parasitic diodes due to fast reverse recovery, further inducing severe oscillation in the [...] Read more.
In the traditional SJ MOSFET structure, n/p pillars with the same doping concentrations in the drift region are introduced to decrease the on-resistance. However, SJ MOSFET will turn on the parasitic diodes due to fast reverse recovery, further inducing severe oscillation in the reverse recovery of the device and the corresponding adverse effect on the circuit. In this study, a fast recovery vertical superjunction (SJ) MOSFET with n-Si and p-3C-SiC pillars was studied. Unlike other structures, such as the 4H-SiC superjunction UMOSFET with a heterojunction diode or the ultra-low recovery charge cell-distributed Schottky contacts SJ-MOSFET with integrated isolated NMOS, we introduce a Schottky barrier diode (SBD) on the source contact at the top of the n-Si pillar in the SJ-MOSFET to improve the device reverse recovery. The simulation software TCAD Silvaco was utilized to simulate the device properties. Compared with the conventional Si SJ, the proposed Si/SiC SJ with the Schottky barrier diode (SBD) connected demonstrated a lower reverse recovery charge, which was reduced by 90.5%, respectively. The waveform of the reverse recovery current demonstrates that the electrons in the device are withdrawn from SBD during reverse recovery, preventing the opening of the parasitic diode in the SJ MOSFET. Finally, another structure is illustrated to decrease the gate capacitance by introducing a thin p-base layer between the gate metal and N-Si pillar so that it can improve the switching characteristics of devices. The open-loss and off-loss of the improved device were reduced by 33% and 42.3%, respectively. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
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11 pages, 3460 KiB  
Article
The Atomic Layer Etching Technique with Surface Treatment Function for InAlN/GaN Heterostructure
by Fangzhou Du, Yang Jiang, Zhanxia Wu, Honghao Lu, Jiaqi He, Chuying Tang, Qiaoyu Hu, Kangyao Wen, Xinyi Tang, Haimin Hong, Hongyu Yu and Qing Wang
Crystals 2022, 12(5), 722; https://doi.org/10.3390/cryst12050722 - 19 May 2022
Cited by 2 | Viewed by 2191
Abstract
This paper studied an atomic layer etching (ALE) technique with a surface treatment function for InAlN/GaN heterostructures with AlN spacer layers. Various parameters were attempted, and 30 s O2 + 15 W BCl3 was chosen as the optimal recipe. The optimal [...] Read more.
This paper studied an atomic layer etching (ALE) technique with a surface treatment function for InAlN/GaN heterostructures with AlN spacer layers. Various parameters were attempted, and 30 s O2 + 15 W BCl3 was chosen as the optimal recipe. The optimal ALE approach exhibited satisfactory etching results, with regard to the etch-stop effect, compared with other techniques. The atomic force microscopy (AFM) results showed an etching per cycle (EPC) value of 0.15 nm/cycle, with a 0.996 fit coefficient and root mean square (RMS) surface roughness of around 0.61 nm (0.71 nm for as-grown sample), which was the lowest in comparison with digital etching (0.69 nm), Cl2/BCl3 continuous etching (0.91 nm) and BCl3 continuous etching (0.89 nm). X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy with energy dispersive X-ray spectroscopy measurements (STEM/EDS) verified the indium clustered phenomena at the bottom apex of V-pit defects in the epi structure of InAlN/GaN high electron mobility transistors (HEMTs) for the first time, in addition to the surface morphology optimization for the ALE under-etching technique used in this work. The resistor hall effect (Hall) and AFM measurements demonstrated that after 4 or 5 ALE cycles, the two-dimensional electron gas (2-DEG) density and RMS roughness were improved by 15% and 11.4%, respectively, while the sheet resistance (Rsh) was reduced by 6.7%, suggesting a good surface treatment function. These findings were important for realizing high-performance InAlN/GaN HEMTs. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
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15 pages, 5007 KiB  
Article
ZnO Films from Thermal Oxidation of Zn Films: Effect of the Thickness of the Precursor Films on the Structural, Morphological, and Optical Properties of the Products
by Oswaldo Sánchez-Dena, Susana Hernández-López, Marco Antonio Camacho-López, Pedro Estanislao Acuña-Ávila, Jorge Alejandro Reyes-Esqueda and Enrique Vigueras-Santiago
Crystals 2022, 12(4), 528; https://doi.org/10.3390/cryst12040528 - 10 Apr 2022
Cited by 1 | Viewed by 1611
Abstract
Zinc oxide (ZnO) films with different structural, morphological, and optical properties were obtained by (fixed) thermal oxidation of deposited metallic zinc (Zn) films. The main characteristics of the oxidized films are discussed in terms of the Zn film thickness. On-axis preferential crystallographic oriented [...] Read more.
Zinc oxide (ZnO) films with different structural, morphological, and optical properties were obtained by (fixed) thermal oxidation of deposited metallic zinc (Zn) films. The main characteristics of the oxidized films are discussed in terms of the Zn film thickness. On-axis preferential crystallographic oriented growth of ZnO can be tuned based on the control of the thickness of the deposited Zn: c-axis (a-axis) for the thinnest (thicker) Zn film. The thicker ZnO film is rather a-textured, whereas the grains hosted by the ZnO films corresponding to the Zn films of intermediate thicknesses are more randomly oriented. For Zn films of ever-increasing thickness, a tendency towards the crystallization of larger ZnO nanocrystals holds, combined with a continuous increment on the surface roughness. In contrast, the fundamental bandgap of the resultant oxide-based films decreases with thickness. The roughness of the ZnO films is not directly measured. It is qualitatively described by the analysis of Zn-film micrographs obtained by Scanning Electron Microscopy and by the demonstration of strong optical scattering interactions present in the thicker ZnO films by their random lasing activity. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
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Review

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32 pages, 7533 KiB  
Review
Research Progress of Micro-LED Display Technology
by Shenghao Zhang, Hua Zheng, Lv Zhou, Huadan Li, Yuanrui Chen, Chenchen Wei, Tao Wu, Wei Lv, Geng Zhang, Shaoqiang Zhang, Zheng Gong, Baohua Jia, Han Lin, Zhiwen Gao, Wei Xu and Honglong Ning
Crystals 2023, 13(7), 1001; https://doi.org/10.3390/cryst13071001 - 23 Jun 2023
Cited by 5 | Viewed by 9021
Abstract
Micro-LED display technology is considered to be the next generation of display technology, which has the characteristics of high miniaturization, thin film and integration, as well as the advantages of high brightness, high contrast, fast response speed and long service life. However, in [...] Read more.
Micro-LED display technology is considered to be the next generation of display technology, which has the characteristics of high miniaturization, thin film and integration, as well as the advantages of high brightness, high contrast, fast response speed and long service life. However, in the development of Micro-LED display technology, there are still some technical and cost problems to be solved. This paper focuses on the key technologies involved in Micro-LED display technology, such as chip technology, mass transfer, full-color display, bonding and driving technology, the research history and frontier progress of these technologies are reviewed in detail. For chip epitaxy technology, the wavelength uniformity, current density and defect control are emphasized; for chip process, the two main chip structures and the challenges brought by miniaturization are discussed emphatically; for chip integration, full-color display, backplane bonding and driving, several mainstream technical schemes are summarized in turn. Finally, the chip detection and repair technologies and commercial application are introduced. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
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16 pages, 2463 KiB  
Review
Research and Progress of Transparent, Flexible Tin Oxide Ultraviolet Photodetector
by Qiannan Ye, Xu Zhang, Rihui Yao, Dongxiang Luo, Xianzhe Liu, Wenxin Zou, Chenxiao Guo, Zhuohui Xu, Honglong Ning and Junbiao Peng
Crystals 2021, 11(12), 1479; https://doi.org/10.3390/cryst11121479 - 28 Nov 2021
Cited by 12 | Viewed by 3261
Abstract
Optical detection is of great significance in various fields such as industry, military, and medical treatment, especially ultraviolet (UV) photodetectors. Moreover, as the demand for wearable devices continues to increase, the UV photodetector, which is one of the most important sensors, has put [...] Read more.
Optical detection is of great significance in various fields such as industry, military, and medical treatment, especially ultraviolet (UV) photodetectors. Moreover, as the demand for wearable devices continues to increase, the UV photodetector, which is one of the most important sensors, has put forward higher requirements for bending resistance, durability, and transparency. Tin oxide (SnO2) has a wide band gap, high ultraviolet exciton gain, etc., and is considered to be an ideal material for preparing UV photodetectors. At present, SnO2-based UV photodetectors have a transparency of more than 70% in the visible light region and also have excellent flexibility of 160% tensile strain. Focusing on SnO2 nanostructures, the article mainly summarizes the progress of SnO2 UV photodetectors in flexibility and transparency in recent years and proposes feasible optimization directions and difficulties. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystals)
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