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Selectivity map for molecular beam epitaxy of advanced III-V quantum nanowire networks
摘要： Selective area growth is a promising technique to enable fabrication of scalable III-V nanowire networks required to test proposals for Majorana-based quantum computing devices. However, the contours of the growth parameter window resulting in selective growth remain undefined. Herein, we present a set of experimental techniques which unambiguously establish the parameter space window resulting in selective III-V nanowire networks growth by molecular beam epitaxy. Selectivity maps are constructed for both GaAs and InAs compounds based on in situ characterization of growth kinetics on GaAs(001) substrates, where the difference in group III adatom desorption rates between the III-V surface and the amorphous mask area is identified as the primary mechanism governing selectivity. The broad applicability of this method is demonstrated by successful realization of high quality InAs and GaAs nanowire networks on GaAs, InP, and InAs substrates of both (001) and (111)B orientations as well as homoepitaxial InSb nanowire networks. Finally, phase coherence in Aharonov-Bohm ring experiments validates the potential of these crystals for nanoelectronics and quantum transport applications. This work should enable faster and better nanoscale crystal engineering over a range of compound semiconductors for improved device performance.
关键词： GaAs,selectivity,selective area growth,epitaxy,InAs,III-V nanowire,molecular beam epitaxy
更新于2025-09-09 09:28:46
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Epitaxial growth of Sb-doped Ge layers on ferromagnetic Fe <sub/>3</sub> Si for vertical semiconductor spintronic devices
摘要： By combining solid phase epitaxy and molecular beam epitaxy with Sb doping, we can form n-type Ge layers on one of the ferromagnetic Heusler alloys, Fe3Si. Two-dimensional epitaxial growth of the Sb-doped Ge layers can be achieved on the Si-terminated Fe3Si surface at 175 ?C. Electrical properties of the Au-Ti/Sb-doped Ge/Fe3Si/p-Ge/Al vertical devices indicate that the Sb-doped Ge layer is an n-type semiconductor. We also show a high-quality CoFe/n-Ge/Fe3Si trilayer structure for vertical semiconductor spintronic devices.
关键词： germanium,solid phase epitaxy,molecular beam epitaxy,spintronics
更新于2025-09-09 09:28:46
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Phase-coherent transport in selectively grown topological insulator nanodots
摘要： Oxidized Si(111) substrates were pre-structured by electron beam lithography and used as a substrate for the selective growth of three-dimensional topological insulators (TI) by molecular beam epitaxy. The patterned holes were filled up by the TI, i.e. Sb2Te3 and Bi2Te3, to form nanodots. Scanning electron microscopy and focused ion beam cross-sectioning was utilized to determine the morphology and depth profile of the nanodots. The magnetotransport measurements revealed universal conductance fluctuations originating from electron interference in phase-coherent loops. We find that these loops are oriented preferentially within the quintuple layers of the TI with only a small perpendicular contribution. Furthermore, we found clear indications of an conductivity anisotropy between different crystal orientations.
关键词： phase-coherent transport,magnetotransport,selective area growth,topological insulators,molecular beam epitaxy
更新于2025-09-09 09:28:46
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Photoconductive antennas based on epitaxial films In <sub/>0.5</sub> Ga <sub/>0.5</sub> As on GaAs (1?1?1)A and (1?0?0)A substrates with a metamorphic buffer
摘要： The terahertz (THz) wave generation by the spiral photoconductive antennas fabricated on the low-temperature and high-temperature grown undoped and Si-doped In0.5Ga0.5As films is studied by the terahertz time-domain spectroscopy method. The In0.5Ga0.5As layers were grown by molecular beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1) A crystallographic orientations utilizing step-graded InxGa1?xAs metamorphic buffer. The antennas are excited by radiation of Er3+-fiber laser at 1.56 μm wavelength in two regimes: with pulse durations of 2.5 ps or 100 fs. It is found that the THz wave generation is 3–4 times more effective in the case of InGaAs-based antennas on (1 1 1)A GaAs substrates as compared to the (1 0 0) substrates. Power-voltage characteristic of the LT-InGaAs antenna up to and beyond threshold breakdown voltage are reported.
关键词： time-domain spectroscopy,terahertz wave generation,photoconductive antenna,GaAs (1 1 1)A,InGaAs,molecular beam epitaxy
更新于2025-09-09 09:28:46
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Engineering SrSnO <sub/>3</sub> Phases and Electron Mobility at Room Temperature Using Epitaxial Strain
摘要： High-speed electronics require epitaxial films with exceptionally high carrier mobility at room temperature. Alkaline-earth stannates with high room-temperature mobility show outstanding prospects for oxide electronics operating at ambient temperatures. However, despite significant progress over the last few years, mobility in stannate films has been limited by dislocations due to the inability to grow fully coherent films. Here, we demonstrate the growth of coherent, strain-engineered phases of epitaxial SrSnO3 (SSO) films using a radical-based molecular beam epitaxy approach. Compressive strain stabilized the high-symmetry tetragonal phase of SSO at room temperature (RT), which, in bulk, exists only at temperatures between 1062 K and 1295 K. We achieved a mobility enhancement of over 300% in doped films compared with the low temperature orthorhombic polymorph. Using comprehensive temperature-dependent synchrotron-based X-ray measurements, electronic transport and first principles calculations, crystal and electronic structures of SSO films were investigated as a function of strain. We argue that strain-engineered films of stannate will enable high mobility oxide electronics operating at RT with the added advantage of being optically transparent.
关键词： phase transition,Hybrid molecular beam epitaxy,half-order diffraction,strain engineering,density functional theory,high mobility,Octahedral rotations
更新于2025-09-09 09:28:46
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High density GaAs nanowire arrays through substrate processing engineering
摘要： GaAs nanowires (NWs) vertically aligned were successfully fabricated through substrate processing engineering. High-density vertical GaAs NWs are grown on n-type Si (111) substrate by molecular beam epitaxy. Systematic experiments indicate that substrate pretreatment is crucial to vertical epitaxial growth of one-dimensional (1D) nanomaterials. The substrates etched using diluted buffered oxide etch (BOE) were explored to improve the NW density and vertical. We also find that the substrate processing engineering strongly affect the morphology of GaAs NWs. Finally, we demonstrate fabrication of GaAs NW arrays on Si surface by field-emission scanning electron microscopy (FE-SEM). This single-step process indeed offers a simple and cost-effective way to obtain a large area of GaAs NW arrays without using e-beam lithography (EBL) and/or nanoimprint lithography (NIL) processes. This work provided a new approach for hight density NW arrays.
关键词： GaAs nanowire arrays,self-catalyzed,buffered oxide etch,molecular beam epitaxy
更新于2025-09-09 09:28:46
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Growth of tr6-CaSi <sub/>2</sub> thin films on Si(111) substrates
摘要： Uniform and high-quality tr6-CaSi2 films were successfully grown via the co-deposition of Ca and Si on a Si(111) substrate. Using reactive Ca deposition, the films tended to form mixed phases of orthorhombic CaSi and two trigonal CaSi2 (three-layer repeat: tr3-CaSi2; six-layer repeat: tr6-CaSi2) structures at low substrate temperatures below 580 °C. A tr6-CaSi2 film was formed when the substrate temperature and thickness of the deposited Ca were controlled. By supplying an external source of Si along with Ca deposition, the formation of CaSi and tr3-CaSi2 was suppressed, and single-phase tr6-CaSi2 was obtained.
关键词： co-deposition,thin films,molecular beam epitaxy,Si(111) substrates,tr6-CaSi2
更新于2025-09-09 09:28:46
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A Scanning Tunneling Microscopy Study of Monolayer and Bilayer Transition-Metal Dichalcogenides Grown by Molecular-Beam Epitaxy
摘要： This review presents an account of some recent scanning tunneling microscopy and spectroscopy (STM/S) studies of monolayer and bilayer transition-metal dichalcogenide (TMD) films grown by molecular-beam epitaxy (MBE). In addition to some intrinsic properties revealed by STM/S, defects such as inversion domain boundaries and point defects, their properties and induced effects, are presented. More specifically, the quantum confinement and moiré potential effects, charge state transition, quasi-particle interference and structural phase transition as revealed by STM/S are described.
关键词： transition-metal dichalcogenides,quantum confinement,structural phase transition,molecular-beam epitaxy,moiré potential,quasi-particle interference,scanning tunneling microscopy,charge state transition
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Kuala Lumpur (2018.8.15-2018.8.17)] 2018 IEEE International Conference on Semiconductor Electronics (ICSE) - Bandgap Engineering of GaAsBi Alloy for Emission of up to 1.52 μm
摘要： Band gap engineering by incorporating bismuth into GaAs to form ternary GaAs1-xBix alloy was investigated. Series of GaAsBi samples with different Bi concentrations were grown by molecular beam epitaxy. Based on high resolution X-ray diffraction (HR-XRD) measurements, Bi concentration of up to 0.108 was successfully incorporated into the lattice. Sample with the highest Bi concentration, GaAs0.892Bi0.108, show room temperature photoluminescence (PL) emission with a peak wavelength of 1.52 μm and full-width-at-half-maximum (FWHM) of 89 meV. It was found that the incorporation of Bi into GaAs lattice affected both the conduction band as well as the valence band. The conduction band minimum reduces linearly by 23 meV/%Bi while the valence band maximum was best fitted by using the valence band anti-crossing (VBAC) model with coupling parameter, CBi of 1.65 eV.
关键词： band gap engineering,X-ray diffraction,molecular beam epitaxy,GaAsBi,photoluminescence
更新于2025-09-09 09:28:46
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Influence of the Quantum Well Structure and Growth Temperature on a Five-Layer InGaMnAs Quantum Well with an InGaAs Buffer Layer
摘要： The in?uence of quantum well structure and growth temperature on a synthesized multilayer system composed of a ?ve-layer InMnGaAs quantum well with an InGaAs buffer layer grown on semi-insulating (100)-oriented substrates prepared by low temperature molecular beam epitaxy was studied. The magnetization measurements using a superconducting quantum interference device indicated the existence of ferromagnetism with a Curie temperature above room temperature in the ?ve-layer InGaMnAs quantum well structure with an InGaAs buffer layer in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements con?rmed the second phase formation of ferromagnetic GaMn clusters. The ferromagnetism that exists in the ?ve-layer of the InMnGaAs quantum well with the InGaAs buffer layer results from a superposition of the ferromagnetism of the low temperature region from the substitutional Mn ions into Ga sites or interstitial Mn ions as well as the presence of manganese ions dopant clusters such as GaMn clusters.
关键词： Molecular Beam Epitaxy,Clusters,Ferromagnetism,Quantum Wells
更新于2025-09-09 09:28:46