A5102943972- Magnetic properties of thin films
- Heusler alloys: electronic and magnetic properties
- Semiconductor Quantum Structures and Devices
- Quantum and electron transport phenomena
- Surface and Thin Film Phenomena
- Semiconductor materials and interfaces
- ZnO doping and properties
- Physics of Superconductivity and Magnetism
- GaN-based semiconductor devices and materials
- Advanced Thermoelectric Materials and Devices
- Topological Materials and Phenomena
- Metal and Thin Film Mechanics
- Acoustic Wave Resonator Technologies
- Magnetic Properties and Applications
- 2D Materials and Applications
- Electronic and Structural Properties of Oxides
- Advanced Materials Characterization Techniques
- Photonic and Optical Devices
- Iron-based superconductors research
- Magnetic and transport properties of perovskites and related materials
- Magnetic Properties of Alloys
- Electron and X-Ray Spectroscopy Techniques
- Rare-earth and actinide compounds
- Ga2O3 and related materials
- Radio Frequency Integrated Circuit Design
Brooke Army Medical Center
2025
University of Wisconsin–Milwaukee
2024
University of Minnesota, Duluth
2001-2024
Johns Hopkins Children's Center
2024
Johns Hopkins University
2024
RTX (United States)
2014-2022
University of California, Santa Barbara
2012-2018
University of Minnesota
2000-2008
University of California, Berkeley
2003
We present a systematic study of the properties room temperature deposited TiN films by varying deposition conditions in an ultra-high-vacuum reactive magnetron sputtering chamber. By increasing pressure from 2 to 9 mTorr while keeping nearly stoichiometric composition Ti1−xNx (x = 0.5) without substrate heating, film resistivity increases, dominant crystal orientation changes (100) (111), grain boundaries become clearer, and strong compressive in-plane strain weak tensile strain. The absorb...
This article presents improvements of large-signal RF power performance at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -band gallium nitride high electron mobility transistors (HEMTs) utilizing a scandium aluminum barrier. Three samples were fabricated and measured having different passivation schemes, including nitride, silicon nitride. The pinning the Fermi level against valence band reduced gain output density passivated device,...
The discovery of topological insulators (TIs), materials with bulk band gaps and protected cross-gap surface states, in compounds such as Bi2Se3 has generated much interest identifying states (TSSs) other classes materials. In particular, recent theory calculations suggest that TSSs may be found half-Heusler ternary compounds. If experimentally realizable, this would provide a platform for entirely new heterostructure spintronic devices make use the structurally-identical but...
Electrical spin injection from Fe into AlxGa1-xAs quantum well heterostructures is demonstrated in small (<500 Oe) in-plane magnetic fields. The measurement sensitive only to the component of that precesses about internal field semiconductor. This much larger than applied and depends strongly on current density. Details observed hysteresis signal are reproduced a model incorporates magnetocrystalline anisotropy epitaxial film, relaxation semiconductor, dynamic polarization nuclei by injected spins.
Electrical spin injection from ferromagnetic δ-MnGa into an (Al,Ga)As p-i-n light-emitting diode (LED) is demonstrated. The layers show strong perpendicular magnetocrystalline anisotropy, enabling detection of at remanence, without applied magnetic field. bias and temperature dependence the are found to be qualitatively similar Fe-based LED devices. A Hanle effect observed demonstrates complete depolarization spins in semiconductor a transverse
Spin injection efficiency is shown to strongly depend on the interfacial structure between Fe contacts and ${\text{Al}}_{\text{x}}{\text{Ga}}_{1\ensuremath{-}\text{x}}\text{As}$ in spin-based light emitting diodes. Both magnitude sign of injected carriers are dependent atomic can be controlled through changes temperature both during following growth. We propose that observed dependence due phase formation resulting from Fe/GaAs reactions. This proposed mechanism consistent with electronic...
Control of zero-field spin splitting is realized in a dual-gated high-quality InAs-AlSb two-dimensional electron gas. Magnetotransport experiments showed clean Shubnikov--de Haas oscillations down to low magnetic fields, and the gate-tuned mobility exceeded $700\phantom{\rule{0.16em}{0ex}}000\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}/\mathrm{V}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$. A clear beating effect was observed magnetoresistance at large potential asymmetry between gates....
Arrays of metallic nanostructures embedded within a semiconducting matrix are great interest for applications in plasmonics, photonic crystals, thermoelectrics, and nanoscale ohmic contacts. We report method growing single crystal arrays semimetallic vertical horizontal ErSb nanorods, nanotrees, nanosheets GaSb matrix. The form simultaneously with the have epitaxial, coherent interfaces no evidence stacking faults or dislocations as observed by high-resolution transmission electron...
A simple model explains the atomic and electronic structure of Heusler surfaces, supported by experiments first-principles theory.
We report on recent progress the development of Scandium Aluminum Nitride (ScAlN) based heterostructure field effect transistors (HFETs). are leveraging enhanced polarization properties ScAlN lattice-matched to Gallium (GaN) produce heterostructures that support very large carrier densities (>3.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> /cm xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). have successfully grown...
Epitaxial ferromagnetic metal - semiconductor heterostructures are investigated using polarization-dependent electroabsorption measurements on GaAs p-type and n-type Schottky diodes with embedded In1-xGaxAs quantum wells. We have conducted studies as a function of photon energy, bias voltage, magnetic field, excitation geometry. For optical pumping circularly polarized light at energies above the band edge GaAs, photocurrents spin polarizations order 1 % flow from to ferromagnet under...
In situ scanning tunneling microscopy and x-ray photoelectron spectroscopy were combined to examine the formation of Fe/GaAs interface for Fe films grown on GaAs(100) As-rich surfaces by molecular beam epitaxy. Scanning images acquired following growth ultrathin layers GaAs (2×4)/c(2×8)β2 show initial results in little disruption As-dimer rows located directly adjacent deposited clusters temperatures between −15 175 °C. X-ray photoemission spectra interfacial Fe–Ga–As reactions depend...
Mn thin films were deposited in situ on molecular beam epitaxy grown GaAs(001) surfaces at 0 °C. Postgrowth anneals of the Mn/GaAs samples done 200, 300, and 400 °C for times ranging from 0.5 to 30 h. Rutherford backscattering spectrometry, x-ray diffraction, transmission electron microscopy show that annealed 300 interfacial reactions initially result formation an epitaxial two phase region (Mn2As MnGa) with average composition Mn0.6Ga0.2As0.2. The rate reaction between GaAs shows a square...
The growth of ErAs on GaAs(001) surfaces occurs by an embedded mode encompassing three steps; (i) island nucleation within the substrate surface, (ii) lateral islands, and (iii) islands into a continuous film. This cannot be modeled in terms epitaxial strain or bulk, interfacial energy differences, which have been used to explain most conventional modes. Instead surface morphologies resulting from this are shown depend structural thermodynamics, diffusion.
The experimental band structure of the rare-earth pnictide erbium arsenide (ErAs), grown epitaxially on GaAs(100), has been mapped out using photoelectron spectroscopy and inverse photoemission spectroscopy. electronic is dominated by bulk bands qualitatively consistent with calculated structure. A number additional nondispersing $4f$ multiplet levels can be identified in valence-band as well at least one surface resonance band. From symmetry selection rules, provides strong evidence that...
We have studied hyperfine interactions between spin-polarized electrons and lattice nuclei in Al_0.1Ga_0.9As/GaAs quantum well (QW) heterostructures. The are electrically injected into the semiconductor heterostructure from a metallic ferromagnet across Schottky tunnel barrier. electron current dynamically polarizes QW, polarized turn alter spin dynamics. steady-state is detected via circular polarization of emitted electroluminescence. nuclear dynamics accurately modeled using formalism...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Jason K. Kawasaki, Linda I. M. Johansson, Brian D. Schultz, Chris J. Palmstrøm; Growth transport properties of epitaxial lattice matched half Heusler CoTiSb/InAlAs/InP(001) heterostructures. Appl. Phys. Lett. 13 January 2014; 104 (2): 022109. https://doi.org/10.1063/1.4862191 Download citation file: Ris...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Sahil J. Patel, Jason K. Kawasaki, John Logan, Brian D. Schultz, Adell, B. Thiagarajan, A. Mikkelsen, Chris Palmstrøm; Surface electronic structure of epitaxial PtLuSb (001) thin films. Appl. Phys. Lett. 19 May 2014; 104 (20): 201603. https://doi.org/10.1063/1.4879475 Download citation file: Ris (Zotero)...
Interfacial reactions between epitaxial films of Fe and GaAs were examined using Rutherford backscattering spectrometry, x-ray diffraction, transmission electron microscopy as a function postgrowth annealing conditions. At 450°C, two stable binary phases observed at the Fe∕GaAs(001) interface with DO3Fe3Ga forming near Fe2As interface. The diffusion rate in reacted was found to be similar magnitude that Ga As resulting rough intermixed interfacial region.
Highly uniform AlGaN/GaN HEMT films with good electron transport properties have been grown on 200-mm silicon substrates by plasma molecular beam epitaxy. X-ray diffraction measurements indicate an AlGaN compositional and thickness variation of ±1% across the wafer, a 29 point resistance map yielded sheet 451 Ω/sq ± 1.1%. The mobility for seven taken diameter wafer was 1555 cm2/Vs 1%. obtained is within 10% GaN HEMTs 100-mm SiC substrates, which much smaller lattice mismatch GaN. were at...
Ferromagnetic bcc-FexCo1−x(100) films have been successfully grown on GaAs(100) and ScyEr1−yAs(100) by molecular beam epitaxy. X-ray diffraction combined with reflection high energy electron low patterns revealed the epitaxial orientation of bcc-FexCo1−x(100)〈010〉‖GaAs(100)〈010〉 〈010〉‖ScyEr1−yAs(100)〈010〉. Rutherford backscattering channeling minimum yields, χmin∼3%, suggest crystalline quality. Vibrating sample magnetometry measurements show in-plane uniaxial anisotropy fourfold for...
The epitaxial growth of ErSb on GaSb(001) surfaces occurs by an embedded mode where stable nanometer sized islands are nucleated within the semiconductor via a displacement reaction surface. extend up to four atomic layers beneath surface before growing laterally and coalescing into continuous film. is not governed strain or surface, bulk, interfacial energy differences, instead morphologies resulting from this shown depend structural similarities, thermodynamics, diffusion.
The Half Heuslers are currently an attractive family of compounds for high temperature thermoelectrics research, and recently, there has been renewed interest since some these proposed to be topological insulators. NiTiSn belongs the 18 valence electron that predicted semiconducting, despite being composed entirely metallic elements. growth Heusler compound by molecular beam epitaxy is demonstrated. films epitaxial single crystalline as observed reflection high-energy diffraction x-ray...