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Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications

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A special issue of Coatings (ISSN 2079-6412). This special issue belongs to the section "Thin Films".

Deadline for manuscript submissions: closed (15 December 2021) | Viewed by 27952

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Special Issue Editor

Dr. Massimo Longo

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Guest Editor

Institute for Microelectronics and Microsystems, National Research Council (CNR-IMM), Agrate Brianza, Italy
Interests: MOCVD; chalcogenides; phase change memories; epitaxy; nanostructures

Special Issue Information

Dear Colleagues,

Metalorganic Chemical Vapor Deposition (MOCVD), introduced by Manasevit in 1968, has been attracting continuous interest, being related to the study and fabrication of many devices, ranging from optoelectronics, microelectronics, sensors, and detectors, to energy harvesting. Nowadays, the scientific and commercial importance of MOCVD is well recognized, since it yields state-of-the art devices that benefit from high process control, and a large variety of good quality materials (either thin films, multilayers, or low-dimensional structures), which can be grown with excellent doping control, large area deposition, and easy industrial transferability. Moreover, being a chemical deposition technique, MOCVD enables conformal growth with relatively low costs and convenient deposition rates, which is particularly useful when the film coating of complex substrate recesses or nanostructures is required. All these advantages cannot be easily found in other advanced deposition techniques. Indeed, different devices of commercial interest are grown by MOCVD, such as light emitting diodes (LEDs), high-efficiency solar cells, and infrared detectors. Efforts to improve the performance of materials and devices grown by MOCVD are being mainly directed toward the realization of better reactors, novel and less harmful chemical precursors, higher material uniformity, implementation of in-situ characterization, and larger area growth.

The scope of this Special Issue is to gather different contributions from different areas of MOCVD research activity, to provide an overview of the most recent results and discoveries, with a special focus on materials functionality, thus providing an update on how this important technique is evolving and what the future trends are. Therefore, contributions will be welcome on the following topics:

III-V and nitride semiconductors and devices;
II-VI semiconductors and devices;
Group IV semiconductors and devices;
IV-V-VI semiconductors and devices;
Functional and smart complex oxides;
Structural and functional coatings;
Epitaxy, multilayered materials, and nanocomposites;
Nanowires and nanodots;
2D materials and Van der Waals heterostructures;
Materials for energy conversion;
Topological insulators, and materials for spintronics;
Materials for information and communication technology;
Surface chemistry, catalyzed growth, and selective area deposition;
Process simulation and in-situ monitoring.

Dr. Massimo Longo
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. Coatings 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

MOCVD
MOVPE
thin films
nanostructures
multilayers
2D materials
functional coatings

Published Papers (11 papers)

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Editorial

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3 pages, 171 KiB

Open AccessEditorial

Special Issue “Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications—Volume II”

by Massimo Longo

Coatings 2023, 13(2), 428; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings13020428 - 14 Feb 2023

Viewed by 1080

Abstract

In our world dominated by global communications, data centers, travels and environmental concerns, there is an increasing need for the deposition of materials with competitive quality, thruput, and relatively low cost/impact, to be implemented in smart devices capable of integrating complex systems, such [...] Read more.

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

Research

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12 pages, 1768 KiB

Open AccessArticle

Comparative Spectroscopic Study of Aluminum Nitride Grown by MOCVD in H₂ and N₂ Reaction Environment

by Samiul Hasan, Mohi Uddin Jewel, Stavros G. Karakalos, Mikhail Gaevski and Iftikhar Ahmad

Coatings 2022, 12(7), 924; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings12070924 - 29 Jun 2022

Cited by 8 | Viewed by 2273

Abstract

We report a comparative spectroscopic study on the thin films of epitaxial aluminum nitride (AlN) on basal plane sapphire (Al₂O₃) substrates grown in hydrogen (H₂) and nitrogen (N₂) gas reaction environments. AlN films of similar thicknesses (~3.0 µm) were grown by metal-organic chemical vapor deposition (MOCVD) for comparison. The impact of the gas environment on the AlN epilayers was characterized using high-resolution X-ray diffraction (HR-XRD), X-ray photoelectron spectroscopy (XPS), Raman scattering (RS), secondary ion mass spectroscopy (SIMS), cathodoluminescence (CL), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The study showed that AlN layers grown in a N₂ environment have 50% less stress (~0.5 GPa) and similar total dislocation densities (~10⁹/cm²) as compared to the films grown in a H₂ environment. On the other hand, AlN films grown in a H₂ gas environment have about 33% lesser carbon and 41% lesser oxygen impurities than films grown in a N₂ growth environment. The possible mechanisms that influenced the structural quality and impurity incorporation for two different gas environments to grow AlN epilayers in the MOCVD system on sapphire substrates were discussed. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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11 pages, 6803 KiB

Open AccessFeature PaperArticle

MOCVD of II-VI HRT/Emitters for V_oc Improvements to CdTe Solar Cells

by Andrew J. Clayton, Ali Abbas, Peter J. Siderfin, Stephen Jones, Ana Teloeken, Ochai Oklobia, John M. Walls and Stuart J. C. Irvine

Coatings 2022, 12(2), 261; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings12020261 - 16 Feb 2022

Cited by 1 | Viewed by 2151

Abstract

CdTe solar cells were produced using metal organic chemical vapour deposition (MOCVD), which employed a (Zn,Al)S (AZS) high resistant transparent (HRT) layer at the transparent conducting oxide (TCO)/Cd(Zn)S emitter interface, to enable the higher annealing temperature of 440 °C to be employed in the chlorine heat treatment (CHT) process. The AZS HRT remained intact with conformal coverage over the TCO after performing the high CHT annealing, confirmed by cross-section scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDX) characterisation, which also revealed the Cd(Zn)S emitter layer having been consumed by the CdTe absorber via interdiffusion. The more aggressive CHT resulted in large CdTe grains. The combination of AZS HRT and aggressive CHT increased open circuit voltage (V_oc) and improved solar cell performance. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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11 pages, 2548 KiB

Open AccessArticle

Plasma-Assisted MOCVD Growth of Non-Polar GaN and AlGaN on Si(111) Substrates Utilizing GaN-AlN Buffer Layer

by Pepen Arifin, Heri Sutanto, Sugianto and Agus Subagio

Coatings 2022, 12(1), 94; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings12010094 - 14 Jan 2022

Cited by 6 | Viewed by 2493

Abstract

We report the growth of non-polar GaN and AlGaN films on Si(111) substrates by plasma-assisted metal-organic chemical vapor deposition (PA-MOCVD). Low-temperature growth of GaN or AlN was used as a buffer layer to overcome the lattice mismatch and thermal expansion coefficient between GaN and Si(111) and GaN’s poor wetting on Si(111). As grown, the buffer layer is amorphous, and it crystalizes during annealing to the growth temperature and then serves as a template for the growth of GaN or AlGaN. We used scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) characterization to investigate the influence of the buffer layer on crystal structure, orientation, and the morphology of GaN. We found that the GaN buffer layer is superior to the AlN buffer layer. The thickness of the GaN buffer layer played a critical role in the crystal quality and plane orientation and in reducing the cracks during the growth of GaN/Si(111) layers. The optimum GaN buffer layer thickness is around 50 nm, and by using the optimized GaN buffer layer, we investigated the growth of AlGaN with varying Al compositions. The morphology of the AlGaN films is flat and homogenous, with less than 1 nm surface roughness, and has preferred orientation in a-axis. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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9 pages, 3320 KiB

Open AccessArticle

MOCVD Growth of GeTe/Sb₂Te₃ Core–Shell Nanowires

by Arun Kumar, Raimondo Cecchini, Claudia Wiemer, Valentina Mussi, Sara De Simone, Raffaella Calarco, Mario Scuderi, Giuseppe Nicotra and Massimo Longo

Coatings 2021, 11(6), 718; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings11060718 - 15 Jun 2021

Cited by 6 | Viewed by 2731

Abstract

We report the self-assembly of core–shell GeTe/Sb₂Te₃ nanowires (NWs) on Si (100), and SiO₂/Si substrates by metalorganic chemical vapour deposition, coupled to the vapour–liquid–solid mechanism, catalyzed by Au nanoparticles. Scanning electron microscopy, X-ray diffraction, micro-Raman mapping, high-resolution transmission electron microscopy, and electron energy loss spectroscopy were employed to investigate the morphology, structure, and composition of the obtained core and core–shell NWs. A single crystalline GeTe core and a polycrystalline Sb₂Te₃ shell formed the NWs, having core and core–shell diameters in the range of 50–130 nm and an average length up to 7 µm. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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13 pages, 3629 KiB

Open AccessArticle

MOCVD Grown HgCdTe Heterostructures for Medium Wave Infrared Detectors

by Waldemar Gawron, Jan Sobieski, Tetiana Manyk, Małgorzata Kopytko, Paweł Madejczyk and Jarosław Rutkowski

Coatings 2021, 11(5), 611; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings11050611 - 20 May 2021

Cited by 10 | Viewed by 3157

Abstract

This paper presents the current status of medium-wave infrared (MWIR) detectors at the Military University of Technology’s Institute of Applied Physics and VIGO System S.A. The metal–organic chemical vapor deposition (MOCVD) technique is a very convenient tool for the deposition of HgCdTe epilayers, with a wide range of compositions, used for uncooled infrared detectors. Good compositional and thickness uniformity was achieved on epilayers grown on 2-in-diameter, low-cost (100) GaAs wafers. Most growth was performed on substrates, which were misoriented from (100) by between 2° and 4° in order to minimize growth defects. The large lattice mismatch between GaAs and HgCdTe required the usage of a CdTe buffer layer. The CdTe (111) B buffer layer growth was enforced by suitable nucleation procedure, based on (100) GaAs substrate annealing in a Te-rich atmosphere prior to the buffer deposition. Secondary-ion mass spectrometry (SIMS) showed that ethyl iodide (EI) and tris(dimethylamino)arsenic (TDMAAs) were stable donor and acceptor dopants, respectively. Fully doped (111) HgCdTe heterostructures were grown in order to investigate the devices’ performance in the 3–5 µm infrared band. The uniqueness of the presented technology manifests in a lack of the necessity of time-consuming and troublesome ex situ annealing. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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13 pages, 7238 KiB

Open AccessArticle

Growth of GaP Layers on Si Substrates in a Standard MOVPE Reactor for Multijunction Solar Cells

by Pablo Caño, Carmen M. Ruiz, Amalia Navarro, Beatriz Galiana, Iván García and Ignacio Rey-Stolle

Coatings 2021, 11(4), 398; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings11040398 - 30 Mar 2021

Cited by 5 | Viewed by 2181

Abstract

Gallium phosphide (GaP) is an ideal candidate to implement a III-V nucleation layer on a silicon substrate. The optimization of this nucleation has been pursued for decades, since it can form a virtual substrate to grow monolithically III-V devices. In this work we present a GaP nucleation approach using a standard MOVPE reactor with regular precursors. This design simplifies the epitaxial growth in comparison to other routines reported, making the manufacturing process converge to an industrial scale. In short, our approach intends to mimic what is done to grow multijunction solar cells on Ge by MOVPE, namely, to develop a growth process that uses a single reactor to manufacture the complete III-V structure, at common MOVPE process temperatures, using conventional precursors. Here, we present the different steps in such GaP nucleation routine, which include the substrate preparation, the nucleation itself and the creation of a p-n junction for a Si bottom cell. The morphological and structural measurements have been made with AFM, SEM, TEM and Raman spectroscopy. These results show a promising surface for subsequent III-V growth with limited roughness and high crystallographic quality. For its part, the electrical characterization reveals that the routine has also formed a p-n junction that can serve as bottom subcell for the multijunction solar cell. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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8 pages, 1766 KiB

Open AccessArticle

Study of the Annealing Effect on the γ-Phase Aluminum Oxide Films Prepared by the High-Vacuum MOCVD System

by Zhao Li, Yangmei Xin, Yunyan Liu, Huiqiang Liu, Dan Yu and Junshan Xiu

Coatings 2021, 11(4), 389; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings11040389 - 29 Mar 2021

Cited by 7 | Viewed by 1827

Abstract

γ-phase aluminum oxide (γ-Al₂O₃) films are grown on MgO (100) wafers by metal organic chemical vapor deposition (MOCVD). Post-annealing process is conducted to study the influence of annealing temperature on the properties of the films. Structural analyses indicate that all the deposited and annealed films present a preferred growth orientation of γ-Al₂O₃ (220) along the MgO (200) direction. And the film annealed at 1100 °C exhibits the best film quality compared with those of the films grown and annealed at other temperatures. Scanning electron microscopy measurements also imply the best surface morphology for the γ-Al₂O₃ film annealed at 1100 °C, which is in good accordance with the structural analyses. Optical transmittance spectra show good transparency for all the deposited and annealed films in the visible wavelength region with an average transmittance value of 83.5%. The optical bandgaps are estimated to be in the range of 5.56–5.79 eV for the deposited and annealed films. Semiconductor films with high optical transmittance in the visible region as well as wide bandgaps are appropriate for the manufacture of transparent optoelectronic devices and ultraviolet optoelectronic devices. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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7 pages, 2036 KiB

Open AccessFeature PaperArticle

Highly Conductive Co-Doped Ga₂O₃:Si-In Grown by MOCVD

by Junhee Lee, Honghyuk Kim, Lakshay Gautam and Manijeh Razeghi

Coatings 2021, 11(3), 287; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings11030287 - 02 Mar 2021

Cited by 8 | Viewed by 2603

Abstract

We report a highly conductive gallium oxide doped with both silicon and indium grown on c-plane sapphire substrate by MOCVD. From a superlattice structure of indium oxide and gallium oxide doped with silicon, we obtained a highly conductive material with an electron hall mobility up to 150 cm²/V·s with the carrier concentration near 2 × 10¹⁷ cm⁻³. However, if not doped with silicon, both Ga₂O₃:In and Ga₂O₃ are highly resistive. Optical and structural characterization techniques such as X-ray, transmission electron microscope, and photoluminescence, reveal no significant incorporation of indium into the superlattice materials, which suggests the indium plays a role of a surfactant passivating electron trapping defect levels. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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11 pages, 1895 KiB

Open AccessArticle

Impact of the Deposition Temperature on the Structural and Electrical Properties of InN Films Grown on Self-Standing Diamond Substrates by Low-Temperature ECR-MOCVD

by Shuaijie Wang, Fuwen Qin, Yizhen Bai, Dong Zhang and Jingdan Zhang

Coatings 2020, 10(12), 1185; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings10121185 - 04 Dec 2020

Cited by 7 | Viewed by 2028

Abstract

The progress of InN semiconductors is still in its infancy compared to GaN-based devices and materials. Herein, InN thin films were grown on self-standing diamond substrates using low-temperature electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD) with inert N₂ used as a nitrogen source. The thermal conductivity of diamond substrates makes the as-grown InN films especially attractive for various optoelectronic applications. Structural and electrical properties which depend on deposition temperature were systematically investigated by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Hall effect measurement. The results indicated that the quality and properties of InN films were significantly influenced by the deposition temperature, and InN films with highly c-axis preferential orientation and surface morphology were obtained at optimized temperatures of 400 °C. Moreover, their electrical properties with deposition temperature were studied, and their tendency was correlated with the dependence on micro- structure and morphology. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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10 pages, 6312 KiB

Open AccessArticle

A Modeling and Experimental Study on the Growth of VCSEL Materials Using an 8 × 6 Inch Planetary MOCVD Reactor

by Yudan Gou, Jun Wang, Yang Cheng, Yintao Guo, Xiao Xiao and Shouhuan Zhou

Coatings 2020, 10(8), 797; https://0-doi-org.brum.beds.ac.uk/10.3390/coatings10080797 - 18 Aug 2020

Cited by 7 | Viewed by 3151

Abstract

VCSEL (vertical cavity surface emitting laser) is a promising optoelectronic device, but its high manufacturing cost limits its scope of applications. Growing on larger size wafers is an effective way to reduce the cost. However, the growth rate uniformity needs to be optimized to ensure the uniformity of the devices’ performance over the wafers. This paper investigates the factors which influence the growth rate uniformity using an 8 × 6 inch planetary reactor through experiments and simulations. At a carrier gas flow rate of 37 slm, an AsH₃ flow rate of 600 sccm, an AsH₃ flow rate ratio of 100:500, and a ceiling temperature of 175 °C, the growth rate uniformity of the AlGaAs layer with a relative standard deviation of 0.16%, 1σ, was obtained over the 6-inch wafers. The uniformity of the DBR stop band center and VCSEL quantum well wavelength with standard deviations of 0.142% and 0.023%, 1σ, were received over the 6-inch wafers, respectively. Based on the optimized results, 99.95% of VCSEL devices with wavelengths of 940 ± 5 nm were realized over the 6-inch wafers. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures by MOCVD: Fabrication, Characterization and Applications)

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