Crystals

Research

14 pages, 4456 KiB

Open AccessEditor’s ChoiceArticle

The Epitaxial Growth of Ge and GeSn Semiconductor Thin Films on C-Plane Sapphire

by Emmanuel Wangila, Calbi Gunder, Petro M. Lytvyn, Mohammad Zamani-Alavijeh, Fernando Maia de Oliveira, Serhii Kryvyi, Hryhorii Stanchu, Aida Sheibani, Yuriy I. Mazur, Shui-Qing Yu and Gregory Salamo

Crystals 2024, 14(5), 414; https://doi.org/10.3390/cryst14050414 - 28 Apr 2024

Cited by 1 | Viewed by 1587

Abstract

Ge_1−xSn_x growth on a new sapphire platform has been demonstrated. This involved the growth of GeSn on Ge/GaAs layers using the algorithm developed. The resultant growths of Ge on GaAs/AlAs/sapphire and Ge_1−xSn_x on Ge/GaAs/AlAs/sapphire were investigated by [...] Read more.

Ge_1−xSn_x growth on a new sapphire platform has been demonstrated. This involved the growth of GeSn on Ge/GaAs layers using the algorithm developed. The resultant growths of Ge on GaAs/AlAs/sapphire and Ge_1−xSn_x on Ge/GaAs/AlAs/sapphire were investigated by in situ and ex situ characterization techniques to ascertain the surface morphology, crystal structure, and quality. The growth mode of Ge on GaAs was predominantly two-dimensional (2D), which signifies a layer-by-layer deposition, contributing to enhanced crystal quality in the Ge/GaAs system. The growth of Ge_1−xSn_x with 10% Sn on a graded profile for 30 min shows uniform composition and a strong peak on the reciprocal space map (RSM). On the other hand, the partially relaxed growth of the alloy on RSM was established. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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9 pages, 4468 KiB

Open AccessArticle

Fabrication of SiC-on-Insulator (SiCOI) Layers by Chemical Vapor Deposition of 3C-SiC on Si-in-Insulator Substrates at Low Deposition Temperatures of 1120 °C

by Johannes Steiner, Jana Schultheiß, Shouzhong Wang and Peter J. Wellmann

Crystals 2023, 13(11), 1590; https://doi.org/10.3390/cryst13111590 - 17 Nov 2023

Cited by 2 | Viewed by 1519

Abstract

Compared to bulk silicon carbide (SiC) wafers, SiC-on-insulator (SiCOI) substrates enable new device designs of electronic switches as well as novel photonic applications. One application is a micro-resonator for the usage in a Kerr frequency comb. For SiCOI substrates, a deposition temperature below [...] Read more.

Compared to bulk silicon carbide (SiC) wafers, SiC-on-insulator (SiCOI) substrates enable new device designs of electronic switches as well as novel photonic applications. One application is a micro-resonator for the usage in a Kerr frequency comb. For SiCOI substrates, a deposition temperature below 1200 °C is advisable due to stability reasons of the buried oxide layer during chemical vapor deposition (CVD) process conditions. To create 3C-SiC-on-insulator layers, a cold-wall CVD reactor was utilized, with propane and silane as the sources for carbon and silicon, respectively. To improve the cracking of the carbon source gas at low temperatures, the inner setup of the utilized cold-wall CVD reactor was changed to a non-water-cooled system. The change of the inner reactor setup was investigated numerically, and the grown epitaxial layers were characterized by Raman, EDX, SEM-imaging and XRD spectroscopy. We demonstrate successful deposition of 3C-SiC epitaxial layer substrates at temperatures below 1200 °C without delamination on SOI. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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20 pages, 3861 KiB

Open AccessEditor’s ChoiceArticle

Systematic Assessment of Phonon and Optical Characteristics for Gas-Source Molecular Beam Epitaxy-Grown InP_1−xSb_x/n-InAs Epifilms

by Devki N. Talwar and Hao-Hsiung Lin

Crystals 2023, 13(9), 1367; https://doi.org/10.3390/cryst13091367 - 11 Sep 2023

Viewed by 1072

Abstract

Experimental and theoretical assessments of phonon and optical characteristics are methodically accomplished for comprehending the vibrational, structural, and electronic behavior of InP_1−xSb_x/n-InAs samples grown by Gas-Source Molecular Beam Epitaxy. While the polarization-dependent Raman scattering measurements revealed InP-like doublet covering [...] Read more.

Experimental and theoretical assessments of phonon and optical characteristics are methodically accomplished for comprehending the vibrational, structural, and electronic behavior of InP_1−xSb_x/n-InAs samples grown by Gas-Source Molecular Beam Epitaxy. While the polarization-dependent Raman scattering measurements revealed InP-like doublet covering optical modes (

ω_{L O}^{I n P} ~

350 cm⁻¹,

ω_{T O}^{I n P} ~

304 cm⁻¹) and phonons activated by disorders and impurities, a single unresolved InSb-like broadband is detected near ~195 cm⁻¹. In InP_1−xSb_x, although no local vibrational (InSb:P; x → 1) and gap modes (InP:Sb; x → 0) are observed, the Raman line shapes exhibited large separation between the optical phonons of its binary counterparts, showing features similar to the phonon density of states, confirming “two-mode-behavior”. Despite the earlier suggestions of large miscibility gaps in InP_1−xSb_x epilayers for x between 0.02 and 0.97, our photoluminescence (PL) results of energy gaps insinuated achieving high-quality single-phase epilayers with x ~ 0.3 in the miscibility gap. Complete sets of model dielectric functions (MDFs) are obtained for simulating the optical constants of binary InP, InSb, and ternary InP_1−xSb_x alloys in the photon energy (0 ≤ E ≤ 6 eV) region. Detailed MDF analyses of refractive indices, extinction coefficients, absorption and reflectance spectra have exhibited results in good agreement with the spectroscopic ellipsometry data. For InP_0.67Sb_0.33 alloy, our calculated lowest energy bandgap E₀ ~ 0.46 eV has validated the existing first-principles calculation and PL data. We feel that our results on Raman scattering, PL measurements, and simulations of optical constants provide valuable information for the vibrational and optical traits of InP_1−xSb_x/n-InAs epilayers and can be extended to many other technologically important materials. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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9 pages, 2106 KiB

Open AccessArticle

Influence of the Arsenic Pressure during Rapid Overgrowth of InAs/GaAs Quantum Dots on Their Photoluminescence Properties

by Sergey Balakirev, Danil Kirichenko, Natalia Chernenko, Nikita Shandyba, Sergey Komarov, Anna Dragunova, Natalia Kryzhanovskaya, Alexey Zhukov and Maxim Solodovnik

Crystals 2023, 13(9), 1358; https://doi.org/10.3390/cryst13091358 - 8 Sep 2023

Cited by 1 | Viewed by 993

Abstract

In this paper, for the first time, we report a strong effect of the arsenic pressure used for the high-rate GaAs capping of self-assembled InAs quantum dots on their optical properties. A 140 nm red shift of the photoluminescence peak position is observed [...] Read more.

In this paper, for the first time, we report a strong effect of the arsenic pressure used for the high-rate GaAs capping of self-assembled InAs quantum dots on their optical properties. A 140 nm red shift of the photoluminescence peak position is observed when the overgrowth arsenic pressure increases threefold. We explain this behavior in terms of different intensities of quantum dot decomposition, which occurs during the overgrowth under different conditions. When the arsenic pressure is sufficiently high, a GaAs capping layer is formed by deposited species with a low impact on initial quantum dots. At a low arsenic pressure, arsenic deficiency leads to the intensive intermixing caused both by the enhanced Ga/In atom exchange and by the consumption of arsenic atoms belonging to quantum dots for the GaAs capping layer formation. As a result of the overgrowth, quantum dots are divided into families with a large (high pressure) and a small (low pressure) average size, yielding long-wave (1.23 µm) and short-wave (1.09 µm) photoluminescence peaks, respectively. Thus, a significant influence of the overgrowth arsenic pressure on the characteristics of InAs quantum dots is evidenced in this study. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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10 pages, 2017 KiB

Open AccessArticle

Probing Boron Vacancy Complexes in h-BN Semi-Bulk Crystals Synthesized by Hydride Vapor Phase Epitaxy

by Zaid Alemoush, Attasit Tingsuwatit, Jing Li, Jingyu Lin and Hongxing Jiang

Crystals 2023, 13(9), 1319; https://doi.org/10.3390/cryst13091319 - 29 Aug 2023

Cited by 3 | Viewed by 1345

Abstract

Hexagonal BN (h-BN) has emerged as an important ultrawide bandgap (UWBG) semiconductor (E_g~6 eV). The crystal growth technologies for producing semi-bulk crystals/epilayers in large wafer sizes and understanding of defect properties lag decades behind conventional III-nitride wide bandgap (WBG) semiconductors. Here [...] Read more.

Hexagonal BN (h-BN) has emerged as an important ultrawide bandgap (UWBG) semiconductor (E_g~6 eV). The crystal growth technologies for producing semi-bulk crystals/epilayers in large wafer sizes and understanding of defect properties lag decades behind conventional III-nitride wide bandgap (WBG) semiconductors. Here we report probing of boron vacancy (V_B)-related defects in freestanding h-BN semi-bulk wafers synthesized by hydride vapor phase epitaxy (HVPE). A photocurrent excitation spectroscopy (PES) was designed to monitor the transport of photoexcited holes from deep-level acceptors. A dominant transition line at 1.66 eV with a side band near 1.62 eV has been directly observed, which matches well with the calculated energy levels of 1.65 for the V_B-H deep acceptor in h-BN. The identification of V_B complexes via PES measurement was further corroborated by the temperature-dependent dark resistivity and secondary ion mass spectrometry measurements. The results presented here suggested that it is necessary to focus on the optimization of V/III ratio during HVPE growth to minimize the generation of V_B-related defects and to improve the overall material quality of h-BN semi-bulk crystals. The work also provided a better understanding of how V_B complexes behave and affect the electronic and optical properties of h-BN. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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13 pages, 3696 KiB

Open AccessArticle

Analysis of Crystalline Defects Caused by Growth on Partially Planarized Spalled (100) GaAs Substrates

by Jacob T. Boyer, Anna K. Braun, Kevin L. Schulte, John Simon, Steven W. Johnston, Harvey L. Guthrey, Myles A. Steiner, Corinne E. Packard and Aaron J. Ptak

Crystals 2023, 13(4), 681; https://doi.org/10.3390/cryst13040681 - 15 Apr 2023

Cited by 1 | Viewed by 1712

Abstract

We analyze the effect of growth on non-(100) surfaces resulting from incomplete planarization of spalled GaAs wafers on the defect structure of GaAs solar cell layers grown by hydride vapor phase epitaxy (HVPE). Controlled spalling of (100)-oriented GaAs has the potential to reduce [...] Read more.

We analyze the effect of growth on non-(100) surfaces resulting from incomplete planarization of spalled GaAs wafers on the defect structure of GaAs solar cell layers grown by hydride vapor phase epitaxy (HVPE). Controlled spalling of (100)-oriented GaAs has the potential to reduce substrate costs for III-V epitaxy; however, it creates regularly faceted surfaces that may complicate the growth of high-quality III-V optoelectronic devices. We leverage the anisotropic growth rate of HVPE to planarize these faceted GaAs substrates, reducing the surface roughness and degree of faceting. We observe degraded solar cell performance and material quality in sample areas where facets are not completely removed. We used dark lock-in thermography and photoluminescence to identify recombination in areas that were not fully planarized. We used cathodoluminescence to identify the presence of extended defects in these regions, which are correlated with bandgap fluctuations in the material. We hypothesize that these defects were created by strain from compositional fluctuations in ternary alloys grown on the faceted surfaces. This work elucidates the potential issues of solar cells grown on faceted surfaces and builds understanding toward realizing high performance III-V photovoltaics with the cost-reduction potential of controlled spalling. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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15 pages, 3852 KiB

Open AccessArticle

Molecular Beam Epitaxy of Twin-Free Bi₂Se₃ and Sb₂Te₃ on In₂Se₃/InP(111)B Virtual Substrates

by Kaushini S. Wickramasinghe, Candice Forrester and Maria C. Tamargo

Crystals 2023, 13(4), 677; https://doi.org/10.3390/cryst13040677 - 14 Apr 2023

Cited by 1 | Viewed by 1825

Abstract

Three-dimensional topological insulators (3D-TIs) are a new generation of materials with insulating bulk and exotic metallic surface states that facilitate a wide variety of ground-breaking applications. However, utilization of the surface channels is often hampered by the presence of crystal defects, such as [...] Read more.

Three-dimensional topological insulators (3D-TIs) are a new generation of materials with insulating bulk and exotic metallic surface states that facilitate a wide variety of ground-breaking applications. However, utilization of the surface channels is often hampered by the presence of crystal defects, such as antisites, vacancies, and twin domains. For terahertz device applications, twinning is shown to be highly deleterious. Previous attempts to reduce twins using technologically important InP(111) substrates have been promising, but have failed to completely suppress twin domains while preserving high structural quality. Here we report growth of twin-free molecular beam epitaxial Bi₂Se₃ and Sb₂Te₃ structures on ultra-thin In₂Se₃ layers formed by a novel selenium passivation technique during the oxide desorption of smooth, non-vicinal InP(111)B substrates, without the use of an indium source. The formation of un-twinned In₂Se₃ provides a favorable template to fully suppress twin domains in 3D-TIs, greatly broadening novel device applications in the terahertz regime. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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9 pages, 623 KiB

Open AccessEditor’s ChoiceArticle

Epitaxial Integration of Dirac Semimetals with Si(001)

by Anthony Rice and Kirstin Alberi

Crystals 2023, 13(4), 578; https://doi.org/10.3390/cryst13040578 - 28 Mar 2023

Viewed by 1299

Abstract

Topological semimetals contain novel combinations of properties that make them useful in a variety of applications, including optoelectronics, spintronics and low energy computing, and catalysis. Although they have been grown with high quality as bulk single crystals, incorporation with semiconductor substrates will ultimately [...] Read more.

Topological semimetals contain novel combinations of properties that make them useful in a variety of applications, including optoelectronics, spintronics and low energy computing, and catalysis. Although they have been grown with high quality as bulk single crystals, incorporation with semiconductor substrates will ultimately be required to maximize their technological reach. Here, epitaxial growth of the Dirac semimetal Cd

_{3}

As

_{2}

on Si(001) is demonstrated through two routes. First, Cd

_{3}

As

_{2}

(112) epilayers are grown on Si(001) via an intermediate CdTe(111) buffer layer. Second, Cd

_{3}

As

_{2}

(112) is grown directly on Si(001). This work sets the foundation for integration of novel semimetal materials with existing CMOS technology. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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11 pages, 5768 KiB

Open AccessArticle

Ultra-High-Speed Growth of GaAs Solar Cells by Triple-Chamber Hydride Vapor Phase Epitaxy

by Ryuji Oshima, Akio Ogura, Yasushi Shoji, Kikuo Makita, Akinori Ubukata, Shuuichi Koseki, Mitsuru Imaizumi and Takeyoshi Sugaya

Crystals 2023, 13(3), 370; https://doi.org/10.3390/cryst13030370 - 21 Feb 2023

Cited by 6 | Viewed by 2206

Abstract

In photovoltaic (PV) power generation, highly efficient III-V solar cells are promising for emerging mobile applications, such as vehicle-integrated PVs. Although hydride vapor phase epitaxy (HVPE) has received attention due to its lower fabrication costs, realization of high throughput performance while maintaining solar-cell [...] Read more.

In photovoltaic (PV) power generation, highly efficient III-V solar cells are promising for emerging mobile applications, such as vehicle-integrated PVs. Although hydride vapor phase epitaxy (HVPE) has received attention due to its lower fabrication costs, realization of high throughput performance while maintaining solar-cell characteristics using this growth method is essential. In this study, the effect of atmospheric-pressure triple-chamber HVPE growth conditions on GaAs solar-cell properties were carefully investigated in conjunction with defect analysis using deep-level transient spectroscopy (DLTS). Based on the analysis on GaAs reaction processes, the suppression of arsine thermal cracking in the HVPE hot-wall reactor was important to achieve fast GaAs growth using a low input V/III ratio. Moreover, the DLTS results revealed that the reduced input V/III ratio was effective in suppressing the generation of EL2 traps, which is a common GaAs midgap complex defect involving arsenic antisites. Although the EL2 trap density increased with the growth rate, the performance of GaAs solar cells that were grown under reduced arsine thermal cracking exhibited almost no considerable cell parameter deterioration at a growth rate of up to 297 μm/h. Consequently, a conversion efficiency of 24% with a high open-circuit voltage of 1.04 V was achieved for the cells that were grown at 200 μm/h. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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Review

Jump to: Research, Other

14 pages, 17950 KiB

Open AccessFeature PaperReview

Microscopic Characteristics of Kinking Phenomenon in Vertically Free-Standing Nanowires

by Zhina Razaghi and Guo-zhen Zhu

Crystals 2023, 13(10), 1459; https://doi.org/10.3390/cryst13101459 - 3 Oct 2023

Viewed by 1463

Abstract

Vertically free-standing nanowires, synthesized through vapor-based growth, can undergo changes in their growth directions known as kinking. These alterations can significantly influence the physical and chemical properties of nanowires, thereby expanding their potential applications. The occurrence of kinks is commonly associated with variations [...] Read more.

Vertically free-standing nanowires, synthesized through vapor-based growth, can undergo changes in their growth directions known as kinking. These alterations can significantly influence the physical and chemical properties of nanowires, thereby expanding their potential applications. The occurrence of kinks is commonly associated with variations in vapor, temperature, seed, and/or their combinations. However, the interplay among different growth factors complicates the identification of the dominating factor and, consequently, limits precise control over nanowire morphology. Theoretical models, incorporating factors like supersaturation, wetting angle, nanowire size, and surface/interface energies tied to growth conditions, have been developed to describe and predict kinking during nanowire growth. While a few pivotal parameters, such as surface/interface energies and wetting angles, can be subtly adjusted through minor alterations in growth conditions, accurately predicting the occurrence of kinks remains a practical challenge. Conversely, in the present review, we attempted to elucidate connections between microscopic aspects, such as changes in composition and the formation of defects, and the nucleation and progression of kinks. This effort aims to construct a predictive framework that enhances our understanding of the tendencies in nanowire growth. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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Other

Jump to: Research, Review

16 pages, 9602 KiB

Open AccessPerspective

Plasmonic Modification of Epitaxial Nanostructures for the Development of a Highly Efficient SERS Platform

by Ewa Dumiszewska, Aleksandra Michałowska, Libor Nozka, Dariusz Czolak and Jan Krajczewski

Crystals 2023, 13(11), 1539; https://doi.org/10.3390/cryst13111539 - 26 Oct 2023

Viewed by 1358

Abstract

Epitaxy is the process of crystallization of monocrystalline layers and nanostructures on a crystalline substrate. It allows for the crystallization of various semiconductor layers on a finite quantity of semiconductor substrates, like GaAs, InP, GaP, InGaP, GaP, and many others. The growth of [...] Read more.

Epitaxy is the process of crystallization of monocrystalline layers and nanostructures on a crystalline substrate. It allows for the crystallization of various semiconductor layers on a finite quantity of semiconductor substrates, like GaAs, InP, GaP, InGaP, GaP, and many others. The growth of epitaxial heterostructures is very complicated and requires special conditions and the precise control of the growth temperature, the pressure in the reactor, and the flow of the precursors. It is used to grow epitaxial structures in lasers, diodes, detectors, photovoltaic structures, and so on. Semiconductors themselves are not suitable materials for application in surface-enhanced Raman spectroscopy (SERS) due to poor plasmonic properties in the UV/VIS range caused by missing free electrons in the conduction band due to the existing band gap. A plasmonic material is added on top of the nanostructured pattern, allowing for the formation of mixed photon–plasmon modes called localized surface plasmon-polaritons which stand behind the SERS effect. Typically, gold and silver are used as functional plasmonic layers. Such materials could be deposited via chemical or physical process. Attention has also been devoted to other plasmonic materials, like ones based on the nitrides of metals. The SERS performance of a functional surface depends both on the response of the plasmonic material and the morphology of the underlying semiconductor epitaxial layer. In the context of SERS, epitaxial growth allows for the fabrication of substrates with well-defined 3D nanostructures and enhanced electromagnetic properties. In this work, we described the possible potential plasmonic modification, composed of various coatings such as noble metals, TiN, and others, of well-developed epitaxial nanostructures for the construction of a new type of highly active SERS platforms. This abstract also highlights the role of epitaxial growth in advancing SERS, focusing on its principles, methods, and impact. Furthermore, this work outlines the potential of epitaxial growth to push the boundaries of SERS. The ability to design substrates with tailored plasmonic properties opens avenues for ultralow concentration detection. Full article

(This article belongs to the Special Issue Epitaxial Growth of Semiconductor Materials and Devices)

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