Hexagonal Nanowire Networks Research Articles

WPG‐Controlled Quantum BDD Circuits with BDD Architecture on GaAs‐Based Hexagonal Nanowire Network Structure

One‐dimensional nanowire quantum devices and basic quantum logic AND and OR unit on hexagonal nanowire units controlled by wrap gate (WPG) were designed and fabricated on GaAs‐based one‐dimensional electron gas (1‐DEG) regular nanowire network with hexagonal topology. These basic quantum logic units worked correctly at 35 K, and clear quantum conductance was achieved on the node device, logic AND circuit unit, and logic OR circuit unit. Binary‐decision‐diagram‐ (BDD‐) based arithmetic logic unit (ALU) is realized on GaAs‐based regular nanowire network with hexagonal topology by the same fabrication method as that of the quantum devices and basic circuits. This BDD‐based ALU circuit worked correctly at room temperature. Since these quantum devices and circuits are basic units of the BDD ALU combinational circuit, the possibility of integrating these quantum devices and basic quantum circuits into the BDD‐based quantum circuit with more complicated structures was discussed. We are prospecting the realization of quantum BDD combinational circuitries with very small of energy consumption and very high density of integration.

Novel Nanowire-Based Flip-Flop Circuit Utilizing Gate-Controlled GaAs Three-Branch Nanowire Junctions

A novel set-reset flip-flop (SR-FF) circuit integrating gate-controlled GaAs three-branch nanowire junctions (TBJs) is designed, fabricated, and characterized. Fundamental logic gates including AND, NOT, and NAND are constructed using Schottky wrap gate (WPG)-controlled TBJs together with inverter circuits that have the same configuration. The present SR-FF circuit is simply designed using a pair of cross-coupled TBJ-based NAND gates. The circuit is successfully fabricated on a GaAs-based hexagonal nanowire network. Its correct operation with a voltage transfer gain larger than unity is demonstrated. Reduction of circuit area and possible operation speed are also discussed.

Fabrication and Characterization of Active and Sequential Circuits Utilizing Schottky-Wrap-Gate-Controlled GaAs Hexagonal Nanowire Network Structures

For realization of hexagonal BDD-based digital systems, active and sequential circuits including inverters, flip flops and ring oscillators are designed and fabricated on GaAs-based hexagonal nanowire networks controlled by Schottky wrap gates (WPGs), and their operations are characterized. Fabricated inverters show comparatively high transfer gain of more than 10. Clear and correct operation of hexagonal set-reset flip flops (SR-FFs) is obtained at room temperature. Fabricated hexagonal D-type flip flop (D-FF) circuits integrating twelve WPG field effect transistors (FETs) show capturing input signal by triggering although the output swing is small. Oscillatory output is successfully obtained in a fabricated 7-stage hexagonal ring oscillator. Obtained results confirm that a good possibility to realize practical digital systems can be implemented by the present circuit approach.

Advances in theoretical models of network science

In this review article, we will summarize the main advances in network science investigated by the CIAE Group of Complex Network in this field. Several theoretical models of network science were proposed and their topological and dynamical properties are reviewed and compared with the other models. Our models mainly include a harmonious unifying hybrid preferential model, a large unifying hybrid network model, a quantum interference network, a hexagonal nanowire network, and a small-world network with the same degree. The models above reveal some new phenomena and findings, which are useful for deeply understanding and investigating complex networks and their applications.

Selective MBE growth of hexagonal networks of trapezoidal and triangular GaAs nanowires on patterned (1 1 1)B substrates

As a combination of novel hardware architecture and novel system architecture for future ultrahigh-density III–V nanodevice LSIs, the authors’ group has recently proposed a hexagonal binary decision diagram (BDD) quantum circuit approach where gate-controlled path switching BDD node devices for a single or few electrons are laid out on a hexagonal nanowire network to realize a logic function. In this paper, attempts are made to establish a method to grow highly dense hexagonal nanowire networks for future BDD circuits by selective molecular beam epitaxy (MBE) on (1 1 1)B substrates. The (1 1 1)B orientation is suitable for BDD architecture because of the basic three-fold symmetry of the BDD node device. The growth experiments showed complex evolution of the cross-sectional structures, and it was explained in terms of kinetics determining facet boundaries. Straight arrays of triangular nanowires with 60 nm base width as well as hexagonal arrays of trapezoidal nanowires with a node density of 7.5×10 6 cm −2 were successfully grown with the aid of computer simulation. The result shows feasibility of growing high-density hexagonal networks of GaAs nanowires with precise control of the shape and size.

TOWARD ULTRA-LOW POWER III-V QUANTUM LARGE SCALE INTEGRATED CIRCUITS FOR UBIQUITOUS NETWORK ERA

In an attempt to realize tiny "knowledge vehicles" called intelligent quantum (IQ) chips for use in the coming ubiquitous network society, this paper presents the present status and future prospects of ultra-small-size and ultra-low-power III-V quantum logic large scale integrated circuits based on a novel hexagonal binary-decision diagram (BDD) quantum circuit architecture. Here, quantum transport in path switching node devices formed on III-V semiconductor-based hexagonal nanowire networks is controlled by nanometer scale Schottky wrap gates (WPGs) to realize arbitrary combinational logic function. Feasibility of the approach is shown through fabrication of basic node devices and various small-scale circuits, and approaches for higher density integration and larger scale circuits are discussed.

Selective Molecular Beam Epitaxy Growth of GaAs Hexagonal Nanowire Networks on (111)B Patterned Substrates

In view of applications to hexagonal binary decision diagram (BDD) quantum circuits, the growth of hexagonal GaAs nanowire networks was attempted by selective molecular beam epitaxy (MBE) on (111)B prepatterned substrates. The basic feasibility of <112>-oriented straight nanowires was first investigated. GaAs nanowires were selectively formed on the top (111)B plane of AlGaAs mesa structures with high uniformity. The lateral width of the wires was determined by two facet boundary planes separating the growth regions on the top and the side facets of the mesa structures. The angle of the boundary planes remained constant during growth, resulting in the wire width being precisely controlled by the thickness of the AlGaAs barrier layer. Then, GaAs/AlGaAs hexagonal nanowire networks were grown on the patterned substrates consisting of three equivalent <112>-oriented wires for a (111)B plane. The results of detailed structural and optical studies showed that highly uniform and smoothly connected hexagonal nanowire networks having threefold symmetry were successfully fabricated by the present selective MBE growth technique.

Formation of high-density GaAs hexagonal nano-wire networks by selective MBE growth on pre-patterned [formula omitted] substrates

Attempts were made to grow high-density GaAs hexagonal nano-wire networks on (0 0 1) patterned substrates by selective molecular beam epitaxy. To form a hexagon, 〈 1 ̄ 1 0〉 - and 〈5 1 0〉 -directions were combined. By the growth of straight wire arrays in each direction, the growth mode, conditions and mechanism were investigated. The wire width was shown to be determined for both directions by the facet boundary planes resulting from the growth rate difference on different facets. By optimizing growth conditions, highly uniform and smoothly connected hexagonal nano-wire networks with a density of 3×10 8 cm −2 were successfully formed.

Characterization and control of surfaces and interfaces for III–V nanoelectronics

Recent progress and issues of characterization and control of surfaces and interfaces as related to III–V nanoelectronics are reviewed. After a brief general review of III–V nanotechnology, a novel hexagonal binary decision diagram (BDD) quantum logic circuit approach is introduced where hexagonal nanowire networks are controlled by nanoscale Schottky gates. For controlled formation of high-density nanostruc-tures, selective molecular beam epitaxy growth is described together with a brief description of a cathodoluminescence-based characterization of buried heterointerfaces. As the key processing issue, problems associated with nanostructure surfaces and Schottky gates are discussed, introducing a recent scanned probe study and attempts to remove Fermi level pinning by a silicon interface control layer.

A single electron binary-decision-diagram quantum logic circuit based on Schottky wrap gate control of a GaAs nanowire hexagon

A novel hexagonal binary-decision-diagram (BDD) quantum logic circuit approach for III-V quantum large scale integrated circuits is proposed and its basic feasibility is demonstrated. In this approach, a III-V hexagonal nanowire network is controlled by Schottky wrap gates (WPGs) to implement BDD logic architecture by path switching. A novel single electron BDD OR logic circuit is successfully fabricated on a GaAs nanowire hexagon and correct circuit operation has been confirmed from 1.5 K to 120 K, showing that the WPG BDD circuit can operate over a wide temperature range by trading off between the power-delay product and the operation temperature.

Fabrication of GaAs-based integrated half and full adders by novel hexagonal BDD quantum circuit approach

Feasibility of a novel hexagonal binary decision diagram (BDD) quantum circuit approach based on Schottky wrap gate (WPG) control of GaAs/AlGaAs hexagonal nanowire network has been demonstrated through fabrication of half adders and full adders. Quantum BDD node devices were designed and realized utilizing WPG-controlled quantum wire (QWR) and single electron switches. BDD half sum and carry elements of a half adder were fabricated by integrating the WPG BDD node devices and they operated correctly through either quantum transport at low temperature or many electron classical transport at room temperature. Successful design of hexagonal BDD full adders for arbitrary bits on a hexagonal network without nanowire crossover and fabrication of QWR-based BDD 2-bit full adder on the AlGaAs/GaAs etched hexagonal nanowire network with node density of 10 7 cm −2 clearly indicated the capability of the present approach for large scale quantum device integration.

GaAs and InGaAs single electron hexagonal nanowire circuits based on binary decision diagram logic architecture

The feasibility of a novel approach for single electron quantum LSIs (Q-LSIs) is investigated. It is based on the binary decision diagram (BDD) logic architecture, using arrays of GaAs and InGaAs single electron BDD node devices formed on hexagonal nanowire networks. Single electron branch switches using nanometer-scale Schottky wrap gates on AlGaAs/GaAs etched nanowires and on InGaAs nanowires by selective MBE growth were fabricated. They showed clear conductance oscillation characteristics controlled by a single electron lateral resonant tunneling. Successful design and fabrication of GaAs-based single electron BDD node devices and circuits including OR logic elements and a 2 bit adder indicates the basic feasibility of realizing single electron Q-LSIs by the novel approach.

III–V quantum devices and circuits based on nanoscale Schottky gate control of hexagonal quantum wire networks

The concept, the present status, key issues and future prospects of a novel hexagonal binary decision diagram (BDD) quantum circuit approach for III–V quantum large-scale integrated circuits (QLSIs) are presented and discussed. In this approach, the BDD logic circuits are implemented on III–V semiconductor-based hexagonal nanowire networks controlled by nanoscale Schottky gates. The hexagonal BDD QLSIs can operate at delay-power products near the quantum limit in the quantum regime as well as in the many-electron classical regime. To demonstrate the feasibility of the present approach, GaAs Schottky wrap gate (WPG)-based single-electron BDD node devices and their integrated circuits were fabricated and their proper operations were confirmed. Selectively grown InGaAs sub-10 nm quantum wires and their hexagonal networks have been investigated to form high-density hexagonal BDD QLSIs operating in the quantum regime at room temperature.

Hexagonal binary decision diagram quantum logic circuits using Schottky in-plane and wrap-gate control of GaAs and InGaAs nanowires

Previously quantum device research has been done on discrete device levels and lacks a clear vision for high density integration. This paper proposes a new, simple and realistic approach for quantum large scale integrated circuits (QLSIs) where a binary-decision diagram (BDD) logic architecture is implemented by BDD node devices based on quantum wire transistors (QWTrs) and single electron transistors (SETs) realized by the Schottky in-plane gate (IPG) and wrap-gate (WPG) control of III–V hexagonal nanowire networks. To investigate the feasibility of the proposed approach, BDD devices having QWTrs were formed on GaAs/AlGaAs etched nanowire patterns. They showed expected complimentary quantized conductance switching as required to achieve operation at delay-power products near the quantum limit. The use of embedded InGaAs honeycomb wire networks grown by selective MBE on InP substrates is proposed for constructing circuits operating in quantum regime at room temperature.