Research

5622 KiB

Open AccessArticle

Optical Characterization of AlAsSb Digital Alloy and Random Alloy on GaSb

by Bor-Chau Juang, Baolai Liang, Dingkun Ren, David L. Prout, Arion F. Chatziioannou and Diana L. Huffaker

Crystals 2017, 7(10), 313; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7100313 - 18 Oct 2017

Cited by 6 | Viewed by 5099

Abstract

III-(As, Sb) alloys are building blocks for various advanced optoelectronic devices, but the growth of their ternary or quaternary materials are commonly limited by spontaneous formation of clusters and phase separations during alloying. Recently, digital alloy growth by molecular beam epitaxy has been [...] Read more.

III-(As, Sb) alloys are building blocks for various advanced optoelectronic devices, but the growth of their ternary or quaternary materials are commonly limited by spontaneous formation of clusters and phase separations during alloying. Recently, digital alloy growth by molecular beam epitaxy has been widely adopted in preference to conventional random alloy growth because of the extra degree of control offered by the ordered alloying. In this article, we provide a comparative study of the optical characteristics of AlAsSb alloys grown lattice-matched to GaSb using both techniques. The sample grown by digital alloy technique showed stronger photoluminescence intensity, narrower peak linewidth, and larger carrier activation energy than the random alloy technique, indicating an improved optical quality with lower density of non-radiative recombination centers. In addition, a relatively long carrier lifetime was observed from the digital alloy sample, consistent with the results obtained from the photoluminescence study. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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3332 KiB

Open AccessFeature PaperArticle

Gas Source Techniques for Molecular Beam Epitaxy of Highly Mismatched Ge Alloys

by Chad A. Stephenson, Miriam Gillett-Kunnath, William A. O’Brien, Robert Kudrawiec and Mark A. Wistey

Crystals 2016, 6(12), 159; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst6120159 - 02 Dec 2016

Cited by 6 | Viewed by 4418

Abstract

Ge and its alloys are attractive candidates for a laser compatible with silicon integrated circuits. Dilute germanium carbide (Ge_1−xC_x) offers a particularly interesting prospect. By using a precursor gas with a Ge₄C core, C can be preferentially [...] Read more.

Ge and its alloys are attractive candidates for a laser compatible with silicon integrated circuits. Dilute germanium carbide (Ge_1−xC_x) offers a particularly interesting prospect. By using a precursor gas with a Ge₄C core, C can be preferentially incorporated in substitutional sites, suppressing interstitial and C cluster defects. We present a method of reproducible and upscalable gas synthesis of tetrakis(germyl)methane, or (H₃Ge)₄C, followed by the design of a hybrid gas/solid-source molecular beam epitaxy system and subsequent growth of defect-free Ge_1−xC_x by molecular beam epitaxy (MBE). Secondary ion mass spectroscopy, transmission electron microscopy and contactless electroreflectance confirm the presence of carbon with very high crystal quality resulting in a decrease in the direct bandgap energy. This technique has broad applicability to growth of highly mismatched alloys by MBE. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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3736 KiB

Open AccessArticle

Temperature-Dependent X-ray Diffraction Measurements of Infrared Superlattices Grown by MBE

by Charles J. Reyner, Arnold M. Kiefer, Gamini Ariyawansa, Joshua M. Duran and John E. Scheihing

Crystals 2016, 6(11), 150; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst6110150 - 17 Nov 2016

Cited by 3 | Viewed by 4985

Abstract

Strained-layer superlattices (SLSs) are an active research topic in the molecular beam epitaxy (MBE) and infrared focal plane array communities. These structures undergo a >500 K temperature change between deposition and operation. As a result, the lattice constants of the substrate and superlattice [...] Read more.

Strained-layer superlattices (SLSs) are an active research topic in the molecular beam epitaxy (MBE) and infrared focal plane array communities. These structures undergo a >500 K temperature change between deposition and operation. As a result, the lattice constants of the substrate and superlattice are expected to change by approximately 0.3%, and at approximately the same rate. However, we present the first temperature-dependent X-ray diffraction (XRD) measurements of SLS material on GaSb and show that the superlattice does not contract in the same manner as the substrate. In both InAs/InAs_0.65Sb_0.35 and In_0.8Ga_0.2As/InAs_0.65Sb_0.35 SLS structures, the apparent out-of-plane strain states of the superlattices switch from tensile at deposition to compressive at operation. These changes have ramifications for material characterization, defect generation, carrier lifetime, and overall device performance of superlattices grown by MBE. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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1018 KiB

Open AccessArticle

Interplay Effect of Excitation and Temperature on Carrier Transfer between Vertically Aligned InAs/GaAs Quantum Dot Pairs

by Yao Liu, Ying Wang, Baolai Liang, Qinglin Guo, Shufang Wang, Guangsheng Fu, Yuriy I. Mazur, Morgan E. Ware and Gregory J. Salamo

Crystals 2016, 6(11), 144; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst6110144 - 10 Nov 2016

Cited by 6 | Viewed by 6039

Abstract

Carrier transfer in vertically-coupled InAs/GaAs quantum dot (QD) pairs is investigated. Photoluminescence (PL) and PL excitation spectra measured at low temperature indicate that the PL peak intensity ratio between the emission from the two sets of QDs—i.e., the relative population of carriers between [...] Read more.

Carrier transfer in vertically-coupled InAs/GaAs quantum dot (QD) pairs is investigated. Photoluminescence (PL) and PL excitation spectra measured at low temperature indicate that the PL peak intensity ratio between the emission from the two sets of QDs—i.e., the relative population of carriers between the two layers of QDs—changes with increasing excitation intensity. Temperature-dependent PL reveals unexpected non-monotonic variations in the peak wavelength and linewidth of the seed layer of QDs with temperature. The PL intensity ratio exhibits a “W” behavior with respect to the temperature due to the interplay between temperature and excitation intensity on the inter-layer carrier transfer. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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Review

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8182 KiB

Open AccessReview

Brief Review of Epitaxy and Emission Properties of GaSb and Related Semiconductors

by Shouzhu Niu, Zhipeng Wei, Xuan Fang, Dengkui Wang, Xinwei Wang, Xian Gao and Rui Chen

Crystals 2017, 7(11), 337; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7110337 - 02 Nov 2017

Cited by 10 | Viewed by 6577

Abstract

Groups III–V semiconductors have received a great deal of attention because of their potential advantages for use in optoelectronic and electronic applications. Gallium antimonide (GaSb) and GaSb-related semiconductors, which exhibit high carrier mobility and a narrow band gap (0.725 eV at 300 K), [...] Read more.

Groups III–V semiconductors have received a great deal of attention because of their potential advantages for use in optoelectronic and electronic applications. Gallium antimonide (GaSb) and GaSb-related semiconductors, which exhibit high carrier mobility and a narrow band gap (0.725 eV at 300 K), have been recognized as suitable candidates for high-performance optoelectronics in the mid-infrared range. However, the performances of the resulting devices are strongly dependent on the structural and emission properties of the materials. Enhancement of the crystal quality, adjustment of the alloy components, and improvement of the emission properties have therefore become the focus of research efforts toward GaSb semiconductors. Molecular beam epitaxy (MBE) is suitable for the large-scale production of GaSb, especially for high crystal quality and beneficial optical properties. We review the recent progress in the epitaxy of GaSb materials, including films and nanostructures composed of GaSb-related alloys and compounds. The emission properties of these materials and their relationships to the alloy components and material structures are also discussed. Specific examples are included to provide insight on the common general physical and optical properties and parameters involved in the synergistic epitaxy processes. In addition, the further directions for the epitaxy of GaSb materials are forecasted. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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7512 KiB

Open AccessReview

Recent Advances on p-Type III-Nitride Nanowires by Molecular Beam Epitaxy

by Songrui Zhao and Zetian Mi

Crystals 2017, 7(9), 268; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7090268 - 01 Sep 2017

Cited by 32 | Viewed by 8004

Abstract

p-Type doping represents a key step towards III-nitride (InN, GaN, AlN) optoelectronic devices. In the past, tremendous efforts have been devoted to obtaining high quality p-type III-nitrides, and extraordinary progress has been made in both materials and device aspects. In this [...] Read more.

p-Type doping represents a key step towards III-nitride (InN, GaN, AlN) optoelectronic devices. In the past, tremendous efforts have been devoted to obtaining high quality p-type III-nitrides, and extraordinary progress has been made in both materials and device aspects. In this article, we intend to discuss a small portion of these processes, focusing on the molecular beam epitaxy (MBE)-grown p-type InN and AlN—two bottleneck material systems that limit the development of III-nitride near-infrared and deep ultraviolet (UV) optoelectronic devices. We will show that by using MBE-grown nanowire structures, the long-lasting p-type doping challenges of InN and AlN can be largely addressed. New aspects of MBE growth of III-nitride nanostructures are also discussed. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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8281 KiB

Open AccessReview

Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

by Lijuan Wang, Liyao Zhang, Li Yue, Dan Liang, Xiren Chen, Yaoyao Li, Pengfei Lu, Jun Shao and Shumin Wang

Crystals 2017, 7(3), 63; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7030063 - 24 Feb 2017

Cited by 72 | Viewed by 9200

Abstract

Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial [...] Read more.

Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial growth of bismide thin films and nanostructures, surface, structural, electric, transport and optic properties of various binaries and bismide alloys, and device applications. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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4447 KiB

Open AccessReview

Topological Insulator Film Growth by Molecular Beam Epitaxy: A Review

by Theresa P. Ginley, Yong Wang and Stephanie Law

Crystals 2016, 6(11), 154; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst6110154 - 23 Nov 2016

Cited by 72 | Viewed by 14786

Abstract

In this article, we will review recent progress in the growth of topological insulator (TI) thin films by molecular beam epitaxy (MBE). The materials we focus on are the V₂-VI₃ family of TIs. These materials are ideally bulk insulating with [...] Read more.

In this article, we will review recent progress in the growth of topological insulator (TI) thin films by molecular beam epitaxy (MBE). The materials we focus on are the V₂-VI₃ family of TIs. These materials are ideally bulk insulating with surface states housing Dirac excitations which are spin-momentum locked. These surface states are interesting for fundamental physics studies (such as the search for Majorana fermions) as well as applications in spintronics and other fields. However, the majority of TI films and bulk crystals exhibit significant bulk conductivity, which obscures these states. In addition, many TI films have a high defect density. This review will discuss progress in reducing the bulk conductivity while increasing the crystal quality. We will describe in detail how growth parameters, substrate choice, and growth technique influence the resulting TI film properties for binary and ternary TIs. We then give an overview of progress in the growth of TI heterostructures. We close by discussing the bright future for TI film growth by MBE. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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Other

Jump to: Research, Review

4233 KiB

Open AccessLetter

Formation of GaAs/GaSb Core-Shell Heterostructured Nanowires Grown by Molecular-Beam Epitaxy

by Dong-Dong Wei, Sui-Xing Shi, Chen Zhou, Xu-Tao Zhang, Ping-Ping Chen, Jing-Tao Xie, Feng Tian and Jin Zou

Crystals 2017, 7(4), 94; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst7040094 - 24 Mar 2017

Cited by 4 | Viewed by 4477

Abstract

In this paper, we demonstrated the growth of GaAs/GaSb core-shell heterostructured nanowires on GaAs substrates, with the assistance of Au catalysts by molecular-beam epitaxy. Time-evolution experiments were designed to study the formation of GaSb shells with different growth times. It was found that, [...] Read more.

In this paper, we demonstrated the growth of GaAs/GaSb core-shell heterostructured nanowires on GaAs substrates, with the assistance of Au catalysts by molecular-beam epitaxy. Time-evolution experiments were designed to study the formation of GaSb shells with different growth times. It was found that, by comparing the morphology of nanowires for various growth times, lateral growth was taking a dominant position since GaSb growth began and bulgy GaSb particles formed on the nanowire tips during the growth. The movement of catalyst Au droplets was witnessed, thus, the radial growth was enhanced by sidewall nucleation under the vapor-solid mechanism due to the lack of driving force for axial growth. Moreover, compositional and structural characteristics of the GaAs/GaSb core-shell heterostructured nanowires were investigated by electron microscopy. Differing from the commonly anticipated result, GaSb shells took a wurzite structure instead of a zinc-blende structure to form the GaAs/GaSb wurzite/wurzite core-shell heterostructured nanowires, which is of interest to the research of band-gap engineering. This study provides a significant insight into the formation of core-shell heterostructured nanowires. Full article

(This article belongs to the Special Issue Current and Future Directions in Crystal Growth by Molecular Beam Epitaxy (MBE))

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