A5068664220- ZnO doping and properties
- Semiconductor Quantum Structures and Devices
- Magnetic and transport properties of perovskites and related materials
- Magneto-Optical Properties and Applications
- Semiconductor materials and devices
- Graphene research and applications
- Advancements in Semiconductor Devices and Circuit Design
- Quantum and electron transport phenomena
- Magnetic properties of thin films
- Phase-change materials and chalcogenides
- Topological Materials and Phenomena
- Surface Roughness and Optical Measurements
- Physics of Superconductivity and Magnetism
- Chalcogenide Semiconductor Thin Films
- Heusler alloys: electronic and magnetic properties
- Semiconductor materials and interfaces
- Electronic and Structural Properties of Oxides
- Electron and X-Ray Spectroscopy Techniques
- Crystal Structures and Properties
- Diamond and Carbon-based Materials Research
- Quantum Dots Synthesis And Properties
- Advancements in Photolithography Techniques
- Inorganic Chemistry and Materials
- Metallurgical and Alloy Processes
- Advanced Condensed Matter Physics
Massachusetts Institute of Technology
2025
The University of Tokyo
2001-2025
NEC (Japan)
2008
Japan Science and Technology Agency
2003-2005
Toshiba (Japan)
2002-2003
We have studied the electronic structure of Mn impurities in GaAs by $2p$ core-level photoemission spectroscopy. From cluster-model analysis assuming neutral $({\mathrm{Mn}}^{3+})$ or negatively ionized $({\mathrm{Mn}}^{2+})$ ground state, parameters been obtained. In either case, $d$ electron number is evaluated to be $\ensuremath{\sim}5$ using obtained parameters, meaning that ${\mathrm{Mn}}^{3+}$ impurity, if it exists, consists ${3d}^{5}$ configuration and a valence hole bound through...
We show that suitably designed magnetic semiconductor heterostructures consisting of Mn delta ($\ensuremath{\delta}$)-doped GaAs and $p$-type AlGaAs layers, in which the locally high concentration moments atoms are controllably overlapped with two-dimensional hole gas wave function, realized remarkably ferromagnetic transition temperatures (${T}_{\mathrm{C}}$). A significant reduction compensative interstitials by varying growth sequence structures followed low-temperature annealing led to...
Magnetic Weyl semimetals attract considerable interest not only for their topological quantum phenomena but also as an emerging materials class realizing anomalous Hall effect in the two-dimensional limit. A shandite compound Co3Sn2S2 with layered kagome-lattices is one such material, where vigorous efforts have been devoted to synthesize crystal. Here, we report a synthesis of thin flakes thickness 250 nm by chemical vapor transport method. We find that this facile bottom-up approach allows...
We have obtained the Mn $3d$ partial density of states in ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ using resonance photoemission technique as well by means difference between and GaAs. observed a strong satellite structure on higher binding energy side main peak, Mn-doped II-VI compounds such ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}.$ Based analysis configuration-interaction calculation for ${\mathrm{MnAs}}_{4}$ cluster, we could ascribe spectral...
Structural, magnetic, and magneto-optical properties of GaAs:MnAs granular thin films have been investigated. Zinc-blende(ZB)-type MnAs clusters were found to be formed by annealing at 500°C with a ramp rate 5°C∕min under nitrogen atmosphere. Magnetic this material ZB-type different from those the NiAs-type hexagonal clusters. The ferromagnetic transition temperature TC ZB type is estimated 360K, which higher than TC(=313K) MnAs.
We have fabricated a multilayer structure consisting of semiconductor-magnetic hybrid material GaAs:MnAs and GaAs/AlAs distributed Bragg reflectors, that is one-dimensional semiconductor-based magnetophotonic crystal. Significant enhancement magneto-optical effect was demonstrated at controlled wavelength room temperature. Magneto-optical spectra this system were well explained by theoretical calculations, the mechanism for shown. Also, required conditions application to optical isolators...
${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As},$ $x=0.043,$ has been grown ex situ on GaAs(100) by low-temperature molecular-beam epitaxy. On the reprepared $p(1\ifmmode\times\else\texttimes\fi{}1)$ surface, resonant photoemission of valence band shows a 20-fold enhancement Mn $3d$ contribution at ${L}_{3}$ edge. The difference spectrum is similar to our previously obtained M edge, in particular strong satellite appears and no clear Fermi edge ruling out weight valence-band...
We have theoretically analyzed semiconductor-waveguide-type optical isolators, which are based on the nonreciprocal loss/gain in magneto-optical waveguide having MnAs nanoclusters embedded an InAlAs matrix. The whole device structure is grown InP substrate and operation wavelength 1.55 μm. In TM mode, more than 119 dB/cm of isolation predicted optimum discussed. Furthermore, we proposed a isolator for TE can realize 36 isolation. Since our waveguide-type isolators composed all...
Ga 1−x Mn x As layers with composition of up to 6.2% are investigated by cross-sectional scanning tunneling microscopy and spectroscopy. We identify in the spectra contributions from MnGa− acceptor states, compensating AsGa2+ donor additional which we suggest be Mni2+ interstitials. On basis observed Fermi level shift a charge carrier compensation analysis, deduce concentration Furthermore, images an inhomogeneous distribution dopant atoms.
We have fabricated semiconductor-based magnetic superlattices (SLs) containing GaAs:MnAs granular material in which MnAs nanoclusters are embedded GaAs, and characterized their structural, optical, magneto-optical properties. SLs consisting of AlAs shown to good crystalline quality excellent compatibility with nonmagnetic GaAs/AlAs heterostructures. The optical transmission properties were improved the SLs, while keeping strong GaAs:MnAs. used these a microcavity as central layer, its was...
We present significant enhancement of magneto-optical effect at room temperature in GaAs with MnAs magnetic nanoclusters sandwiched by GaAs/AlAs multilayers acting as distributed Bragg reflectors. The experimentally observed transmissivity and spectra are well explained theoretical calculations. This new material system will open up the possibility realizing nonreciprocal devices integrated semiconductor optoelectronic circuits.
For the first time, we demonstrate standard cell gate density of 3650 KGate/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and SRAM 0.124 mum for 32 nm CMOS platform technology. Both advanced single exposure (SE) lithography gate-first metal gate/high-k (MG/HK) process contribute to reduce total cost per function by 50% from 45 technology node, which is unattainable dual (DE) or double patterning (DP) poly/SiON stack.
The intrinsic Hall effect allows for the generation of a nondissipative charge neutral current, such as pure spin current generated via effect. Breaking spatial inversion or time reversal symmetries, spin-orbit interaction is generally considered necessary current. Here, we challenge this general concept and present detection in centrosymmetric material with little interaction. We employ bilayer graphene, find enhanced nonlocal transport quantum antiferromagnetic state, where spontaneous...
The physics of superconductivity in magic-angle twisted bilayer graphene (MATBG) is a topic keen interest moir\'e systems research, and it may provide insight into the pairing mechanism other strongly correlated materials such as high-$T_{\mathrm{c}}$ superconductors. Here, we use DC-transport microwave circuit quantum electrodynamics (cQED) to measure directly superfluid stiffness superconducting MATBG via its kinetic inductance. We find be much larger than expected from conventional...
The phenomenon of chirality-induced spin selectivity (CISS) refers to the coupling between structural chirality and polarization conduction electrons. While previous studies CISS have primarily focused on systems exhibiting charge current flow, our investigation aims explore within a charge-current-free environment. This approach is intended overcome challenges posed by pinholes in chiral molecular films. In this study, we investigated Gilbert damping NiFe layers deposited two-dimensional...
New embedded DRAM technology for 0.18 /spl mu/m SOC (system on a chip) using the self-aligned salicide block (SSB) process is proposed. This provides full compatibility with high performance logic and minimum number of steps, resulting in low cost short TAT (turnaround time). We fabricated array macro this Co salicide, dual work function gate aluminum bitline processes, confirmed excellent retention characteristics by negative wordline bias scheme.
The quantum Hall system can be used to study many-body physics owing its multiple internal electronic degrees of freedom and tunability. While phase transitions have been studied intensively, research on the temperature-induced this is limited. We measured pure bulk conductivity a antiferromagnetic state in bilayer graphene over wide range temperatures revealed two-step transition associated with breaking long-range order short-range order. Our findings are fundamental understanding electron...
This paper demonstrates a process integration for high performance and small footprint embedded DRAMs. A trench capacitor cell self-aligned bit line contact are selected to maintain exactly the same size as commodity DRAM cells. The array region is covered with thin SiN barrier against salicidation. Ti-salicide source/drain used in logic region. No retention time degradation good circuit confirmed.
Recently spin-transistors receive considerable attention as a highly-functional building block of future integrated circuits. In order to realize spin-transistors, it is essential that technology efficient spin injection/detection for semiconductor channel established. However, this not so easy challenge owing ferromagnet/semiconductor-interface-related several problems. paper, we demonstrate pseudo-spin-MOSFET (PS-MOSFET) architecture new circuit approach using an ordinary MOSFET and...
We calculated the magneto-optical properties of semiconductor-based multilayer structures containing GaAs:MnAs nanoclusters sandwiched by GaAs/AlAs distributed Bragg reflectors (DBRs). Very large Kerr effects (Kerr rotation and ellipticity) are predicted in multilayers with suitable DBR numbers. On basis calculation, we have grown molecular beam epitaxy, demonstrated a effect (more than 600 mdeg at designed wavelength ∼980 nm under relatively low magnetic field room temperature. This III-V...
A new fabrication method for embedded DRAM of 0.18 /spl mu/m generation is proposed, which realizes full compatibility with logic process such as Co salicide, dual work function gate, small thermal budget and metalization, introduces Self-aligned Salicide Block (SSB), a technology. Fabricated shows excellent characteristics respect to both retention time MOSFET AC/DC performance, promising high performance SOC (System On Chip) applications.
The author studies developments in epitaxial ferromagnetic heterostructures based on semiconductors towards spintronics and also presents a magnetotransport study III-V semiconductor with high Curie temperature T/sub c/.