Doubling the mobility of InAs/InGaAs selective area grown nanowires

Selective area growth (SAG) of nanowires and networks promise a route toward scalable electronics, photonics, and quantum devices based on III-V semiconductor materials. The potential of high-mobility SAG nanowires however is not yet fully realised, since interfacial roughness, misfit dislocations at the nanowire/substrate interface and nonuniform composition due to material intermixing all scatter electrons. Here, we explore SAG of highly lattice-mismatched InAs nanowires on insulating GaAs(001) substrates and address these key challenges. Atomically smooth nanowire/substrate interfaces are achieved with the use of atomic hydrogen (a-H) as an alternative to conventional thermal annealing for the native oxide removal. The problem of high lattice mismatch is addressed through an InxGa1-xAs buffer layer introduced between the InAs transport channel and the GaAs substrate. The Ga-In material intermixing observed in both the buffer layer and the channel is inhibited via careful tuning of the growth temperature. Performing scanning transmission electron microscopy and x-ray diffraction analysis along with low-temperature transport measurements we show that optimized In-rich buffer layers promote high-quality InAs transport channels with the field-effect electron mobility over 10 000 cm2 V-1 s-1. This is twice as high as for nonoptimized samples and among the highest reported for InAs selective area grown nanostructures.The project was supported by Microsoft Quantum, the European Research Council (ERC) under Grant No. 716655 (HEMs-DAM), and the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant No. 722176. The authors acknowledge Dr. Keita Ohtani for technical support and fruitful discussions. D.V.B. is grateful to Dr. Juan-Carlos Estrada Saldaña for careful reading of the manuscript. The authors thank Francesco Montalenti, Marco Albani and Leo Miglio for scientific discussions. ICN2 acknowledges funding from Generalitat de Catalunya 2017 SGR 327. ICN2 is supported by the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2017-0706) and is funded by the CERCA Programme/Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science Ph.D. program. The HAADF-STEM microscopy was conducted in the Laboratorio de Microscopias Avanzadas at Instituto de Nanociencia de Aragon-Universidad de Zaragoza. M.C.S. has received funding from the European Unionâs Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 754510 (PROBIST). The funding agency is Consejo Superior de Investigaciones Científicas (CSIC) and the project reference is “Research Platform on Quantum Technologies PTI-001”

Influence of Sr Content on CMR Effect in Polycrystalline La1−xSrxMnO3La_{1-x}Sr_{x}MnO_{3} Thin Films

The magnetoresistance of thin polycrystalline $La_{1-x}Sr_{x}MnO_{3}$ films deposited on lucalox substrate using metal organic chemical vapor deposition technique was investigated in pulsed magnetic fields up to 18 T in the temperature range 100-320 K. The influence of film preparation conditions, ambient temperature variation and Sr content is analyzed in order to determine the optimal conditions for the design of CMR-B-scalar magnetic field sensor based on thin manganite film, operating at room temperature

Growth and Investigation of p−La2//3Ca1//3MnO3p-La_{2//3}Ca_{1//3}MnO_3/n-Si Heterostructures

We report the fabrication and investigation of p-n diode structures based on thin hole-doped $La_{2//3}Ca_{1//3}MnO_3$ films grown on n-type silicon substrates. $La_{2//3}Ca_{1//3}MnO_3$ films with typical thickness of about 400 nm were prepared using pulsed laser deposition. Reflection high-energy electron diffraction measurements revealed polycrystalline quality of $La_{2//3}Ca_{1//3}MnO_3$ thin films on Si substrates. The surface roughness of $La_{2//3}Ca_{1//3}MnO_3$ films investigated by atomic force microscopy was found to be in the range of 25÷30 nm. Studies of electrical properties showed that $La_{2//3}Ca_{1//3}MnO_3$/Si heterostructures exhibit nonlinear asymmetric I-V characteristics both at room temperature and at 78 K. Furthemore, it was shown that these I-V dependences are sensitive to magnetic field, especially at lower voltages

Magneto- and Electroresistance of Ultrathin Anisotropically Strained La-Sr-MnO Films

The magnetoresistance anisotropy of ultrathin La$\text{}_{0.83}$Sr$\text{}_{0.17}$Mn O$\text{}_{3}$ films deposited on NdGaO$\text{}_{3}$ substrate by metalorganic chemical vapour deposition technique was investigated. The electric-field-induced resistance change was studied up to electric fields of 10 kV/cm using ns duration electrical pulses. It was found that in ultrathin (< 10 nm) and thin (< 50 nm) films the origin of electric-field-induced resistance change is thermal. However, the films with thicknesses of about 20 nm, exhibit negative electric-field-induced resistance change, having a pure electronic nature. This effect is explained in terms of two-layer systems with imperfections located at the interface between the layers

Electroresistance of La-Ca-MnO Thin Films

Epitaxial, textured, and polycrystalline La$\text{}_{0.7}$Ca$\text{}_{0.3}$Mn O$\text{}_{3}$ films, having about 150 nm thickness, were prepared by pulsed laser deposition techniques onto (110) NdGaO$\text{}_{3}$, MgO and lucalox substrates and investigated using 10 ns duration, 0.5 ns rise time electrical pulses having amplitude up to 500 V. Electroresistance of the films [R(E)-R(0)]/R(0) was investigated up to 80 kV/cm electric field strengths in temperatures ranging from 300 K to 4.2 K. Strong (up to 93%) negative electroresistance was obtained in polycrystalline La$\text{}_{0.7}$Ca$\text{}_{0.3}$MnO$\text{}_{3}$ films prepared on MgO and lucalox substrates. The epitaxial films grown on NdGaO$\text{}_{3}$ substrate demonstrated only a small resistance change due to Joule heating induced by a current pulse. It was concluded that electroresistance manifests itself in strongly inhomogeneous manganites films exhibiting a large number of structural imperfections producing ferromagnetic tunnel junction nets

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Electron Transport in Modulation-Doped InAlAs/InGaAs/InAlAs Heterostructures in High Electric Fields

The following peculiarities of electron transport in $In_{0.53}Ga_{0.47}As//In_{0.52}Al_{0.48}As$ quantum wells with δ-Si-doped $In_{0.52}Al_{0.48}As$ barriers at high electric fields are discovered: (1) an enhancement of electron mobility by inserting the InAs phonon wall into the $In_{0.53}Ga_{0.47}As//In_{0.52}Al_{0.48}As$ quantum well, as well as increasing the InAs content in the modulation-doped $In_{0.8}Ga_{0.2}As//In_{0.7}Al_{0.3}As$ heterostructure; (2) a large decrease in electron mobility and a change of electron density with increasing electric field in the range of 1-4 kV/cm; (3) a magnetic field dependence of the threshold electric field for intervalley scattering of electrons; and (4) microwave current oscillations in high electric fields

Manganite sensor for measurements of magnetic field disturbances of pulsed actuators

Magnetic field sensors based on polycrystalline Lao Si-o.ipMnt films were used to measure the magnetic field distribution and disturbances during the operation of an electromagnetic launcher. Hollow cylinders made from dural aluminum and iron were used as propelled objects inside the solenoidal coil. The obtained results revealed the ability of manganite sensors to rapidly measure changing high magnetic fields of arbitrary waveforms