Side Gate Research Articles

Electric field geometries dominate quantum transport coupling in silicon nanoring

Investigations on the relation between the geometries of silicon nanodevices and the quantum phenomenon they exhibit, such as the Aharonov–Bohm (AB) effect and the Coulomb blockade, were conducted. An arsenic doped silicon nanoring coupled with a nanowire by electron beam lithography was fabricated. At 1.47 K, Coulomb blockade oscillations were observed under modulation from the top gate voltage, and a periodic AB oscillation of ΔB = 0.178 T was estimated for a ring radius of 86 nm under a high sweeping magnetic field. Modulating the flat top gate and the pointed side gate was performed to cluster and separate the many electron quantum dots, which demonstrated that quantum confinement and interference effects coexisted in the doped silicon nanoring.

Enhancement of Electron–Phonon Interaction by Band-Gap Opening in Bilayer Graphene

Electronic states and phonon energies in bilayer graphene were investigated by electrical and optical measurements under an external electric field, which was controlled by applying bias voltages to a bottom gate and a transparent ionic liquid side gate in a field-effect transistor. The transport measurements showed that the band gap was opened. The symmetric and antisymmetric optical phonons were visible in the Raman scattering spectra. Their behavior was explained by a Kohn anomaly. The mixing of symmetric and antisymmetric optical phonons was minimized by the external electric field, owing to the enhancement of electron–phonon interactions that accompanied the band-gap opening.

Negative quantum capacitance in graphene nanoribbons with lateral gates

We present numerical simulations of the capacitive coupling between graphene nanoribbons of various widths and gate electrodes in different configurations. We compare the influence of lateral metallic or graphene side gate structures on the overall back gate capacitive coupling. Most interestingly, we find a complex interplay between quantum capacitance effects in the graphene nanoribbon and the lateral graphene side gates, giving rise to an unconventional negative quantum capacitance. The emerging non-linear capacitive couplings are investigated in detail. The experimentally relevant relative lever arm, the ratio between the coupling of the different gate structures, is discussed.

Side gate AlGaN/GaN FET on silicon and sapphire

AbstractAlGaN/GaN heterostructures were grown on sapphire and alternatively on silicon substrates covered with a thin SiC layer by MOCVD. The side gated transistors were fabricated using electron beam lithography. The conductivity of the drain‐source branch could be tuned via the side gate formed by a two‐dimensional electron gas directly connected to the source drain branch or separated by a trench.The electrical measurements of the fabricated in‐plane‐gated devices revealed unipolar transistor behavior for both types of substrates. The transconductance was 1 µA/V and the output conductance reached 1.9 µA/V for the side gate transisitor on sapphire. The transconductance and output conductance of the side gate device on silicon substrates were 6 and 18 µA/V, respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Thermal analysis of self-heating in saddle MOSFET devices

The self-heating effects (SHEs) of saddle metal–oxide–semiconductor field-effect transistors (MOSFETs) and gate dimensional impacts on thermal characteristics have been investigated on the basis of a realistic thermal conductivity of silicon and other materials. Thermal characteristics were analyzed by thermal resistance of Si channel. Since Si material has larger thermal conductivity than that of silicon dioxide, it is shown that the length of the side gate of saddle MOSFETs determines heat dissipation of Si channel. Side gate of saddle MOSFETs can be one of the important parameter in device optimization.

화장품 용기의 유동 특성 및 사출금형 제작에 관한 연구

화장품제조업은 동일한 제품을 대량으로 생산하고 소비되는 구조로 금형을 통한 생산은 필연적이다. 화장품을 담는 용기는 소비자의 구매의사에도 영향을 주는 요소이며 완제품가격에서 차지하는 부분이 크기 때문에 경제성, 심미성과 기능성을 충족시키는 금형이 필요하다. 화장품 용기 중에 사각형태의 용기는 미성형 불량이 다른 형태의 제품보다 자주 발생하는 특징을 가진다. 기존에 사각형 형태의 화장품용기 제작공정은 2단 금형에 사이드게이트 구조로 금형을 제작하는데 이는 후가공과 게이트 흔적이 남는 단점이 있다. 본 연구에서 제안한 오버랩게이트는 후가공이 거의 없고 음각으로 게이트가 절단되는 특징이 있으며, 사이드게이트와 비교하여 Moldflow를 이용한 유동시스템을 시뮬레이션 하였다. 오버랩게이트가 유동성, 고화, 밀도, 에어트랩 등에서 유동성 향상과 불량률을 낮출 수 있는 결과를 확인하였으며, 해석결과를 기반으로 금형을 제작을 하고 사출성형 하였다. 본 연구를 통해 미성형 불량을 줄이고 심미성, 기능성 등의 특성을 가지는 화장품용기 제품의 대량생산 가능성을 검증하였다 A cosmetic manufacturing process requires a mold that is inevitable for mass production. Cosmetic containers are one of major factors affecting the customer's purchase decision. In addition, the manufacturing cost in cosmetic container comprises a large portion of the entire product cost. Therefore, a mold satisfying the economical feasibility, aesthetics and functionality is necessary. Among the cosmetic containers, square shape containers have a tendency of having a short shot defect product. The square shaped cosmetic containers are mostly produced as a side gate shape on the two-plate molds. On the other hand, there are two disadvantages, such as gate trace and post processing requirement. The overlap-gateproposed in this study has the characteristics of intaglio gate cutting and no need for post processing. The delivery system of the overlap gate was simulated and compared with the side gate via Moldflow. The improvement in flow, frozen rate, density, and Air trap was confirmed. Based on the simulation results, the mold and performed injection molding was fabricated. In this study, the possibility of the mass production of high aesthetic and functionality cosmetic containers was verified.

Low-frequency noise in individual carbon nanotube field-effect transistors with top, side and back gate configurations: effect of gamma irradiation

We report on the influence of low gamma irradiation (104 Gy) on the noise properties of individual carbon nanotube (CNT) field-effect transistors (FETs) with different gate configurations and two different dielectric layers, SiO2 and Al2O3. Before treatment, strong generation–recombination (GR) noise components are observed. These data are used to identify several charge traps related to dielectric layers of the FETs by determining their activation energy. Investigation of samples with a single SiO2 dielectric layer as well as with two dielectric layers allows us to separate traps for each of the two dielectric layers. We reveal that each charge trap level observed in the side gate operation splits into two levels in top gate operation due to a different potential profile along the CNT channel. After gamma irradiation, only reduced flicker noise is registered in the noise spectra, which indicates a decrease of the number of charge traps. The mobility, which is estimated to be larger than 2 × 104 cm2 V−1 s−1 at room temperature, decreases only slightly after radiation treatment, demonstrating high radiation hardness of the CNTs. Finally, we study the influence of Schottky barriers at the metal–nanotube interface on the transport properties of FETs, analyzing the behavior of the flicker noise component.

Sub-10 nm patterning by focused He-ion beam milling for fabrication of downscaled graphene nano devices

In this work, a novel hybrid fabrication method for graphene quantum dot devices with minimum feature sizes of ∼3nm and high yield is described. It is a combination of e-beam lithography and direct milling with the sub-nm focused helium ion beam generated by a helium ion microscope. The method is used to fabricate graphene quantum dot devices contacted with metal to allow electrical characterization. An annealing step is described that reduces hydrocarbon contamination on the sample surface and allows complete removal of graphene by the helium ion beam and therefore successful isolation of side gates. The electrical characterization of the final device demonstrates the successful fabrication of the first electrically characterized He-ion beam patterned graphene device. The highly controllable, fine scale fabrication capabilities offered by this approach could lead to a more detailed understanding of the electrical characteristics of graphene quantum devices and pave the way towards room-temperature operable graphene quantum dot devices.

AlGaN/GaN Three-Terminal Junction Devices for Rectification and Transistor Applications on 3C-SiC/Si Pseudosubstrates

AlGaN/GaN heterosystems with their two dimensional electron gas at the interface enable high-mobility transistor devices. We present a technology for high-mobility three-terminal junction (TTJ) devices on 3C-SiC(111)/Si(111) pseudosubstrates. Those devices that allow multipurpose applications are determined by only slight variations in their geometrical properties such as side gate transistor behavior besides positive and negative type rectifications on a single chip based on AlGaN/GaN heterostructures grown on silicon substrates using a SiC transition layer. In this paper, we present the technological process and the nonlinear electrical properties of TTJ devices using Si basic substrates with room temperature electron mobility up to 1680 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V s. Narrow and wide bar types of rectifying devices with T and Y type active regions are shown as well as side gate transistors with a transconductance of 20 mS/mm and an output conductance of 600 mS/mm. The TTJ active region withstands fields .

Dual material gate junctionless tunnel field effect transistor

This paper proposes a junctionless tunnel field effect transistor (JLTFET) with dual material gate (DMG) structure and the performance was studied on the basis of energy band profile modulation. The two-dimensional simulation was carried out to show the effect of conduction band minima on the abruptness of transition between the ON and OFF states, which results in low subthreshold slope (SS). Appropriate selection of work function for source and drain side gate metal of a double metal gate JLTFET can also significantly reduce the subthreshold slope (SS), OFF state leakage and hence gives improved I ON/I OFF.

Observation of Side-Gating Effect in AlGaN/GaN Heterostructure Field Effect Transistors

The side-gating effect was demonstrated in AlGaN/GaN heterostructure field effect transistors (HFETs) for the first time. Using 10-µm-thick i-GaN buffer layers, drain currents decreased significantly with the application of a negative bias on a side gate 8 µm away from the FET. The transient responses with LED illumination demonstrated half-recovery condition that can be interpreted as a negative-charge redistribution through a hole emission from traps. The application of a positive side-gate bias confirmed the half-recovery mechanism. From the temperature variation measurements, the trap energy level is estimated to be 0.76 eV from the valence band with a hole capture cross section of approximately 4×10-16 cm2. All these results indicate that the side-gating effect is caused by hole traps in the i-GaN layer, which is in accord with the Shockley–Read–Hall model of deep traps.

Hysteresis in the conductance of asymmetrically biased GaAs quantum point contacts with in-plane side gates

We have observed hysteresis between the forward and reverse sweeps of a common mode bias applied to the two in-plane side gates of an asymmetrically biased GaAs quantum point contact (QPC). The size of the hysteresis loop increases with the amount of bias asymmetry ΔVg between the two side gates and depends on the polarity of ΔVg. Our results are in qualitative agreement with Non-Equilibrium Green's Function simulations including the effects of dangling bond scattering on the sidewalls of the QPC. It is argued that hysteresis may constitute another indirect proof of spontaneous spin polarization in the narrow portion of the QPC.

Voltage difference engineering in SOI MOSFETs: A novel side gate device with improved electrical performance

We studied the impact of voltage difference engineering in a silicon-on-insulator metal oxide semiconductor field-effect transistor (SOI-MOSFET) and compared the performance to that of a conventional SOI-MOSFET (C-SOI). Our structure, called a SIG-SOI MOSFET, includes main and side gates with an optimum voltage difference between them. The voltage difference leads to an inverted channel as an electrical drain extension under the side gate. This channel creates a stepped potential distribution along the channel that it cannot be seen in the C-SOI MOSFETs. The voltage difference controls the channel properly and two-dimensional two-carrier device simulations revealed lower threshold voltage variations, larger breakdown voltage, higher voltage gain, lower hot carrier effects, improved drain-induced barrier lowering, lower drain conductance, higher unilateral power gain, and lower leakage current compared to a C-SOI device. Thus, our proposed structure has higher performance than a typical C-SOI structure.

A novel 4H–SiC MESFET with recessed gate and channel

New structures named as recessed gate and channel (RGC) silicon carbide (SiC) based metal semiconductor field effect transistors (MESFETs) are reported in this paper, in which the gate is recessed into the channel, and the channel is recessed into the p-buffer layer at the source and/or the drain side. Important parameters such as short channel effect, maximum DC trans-conductance (gm), drain current, breakdown voltage and output resistance of the proposed structures are simulated and compared with the conventional 4H–SiC MESFET. Simulation results disclose that, compared to the conventional structure, the structure with recessed full gate and channel (FGC):1.Improves the DC trans-conductance (gm).2.Increases the output resistance.3.Enhances the breakdown voltage.4.Reduces the short channel effect.Moreover, source side recessed gate and drain side recessed channel (SG–DC) structure has higher gm and output resistance in comparison with the conventional structure. Drain side recessed gate and source side recessed channel (DG–SC) structure has larger breakdown voltage and drain current than those of the conventional structure.

Three-Terminal Single-Molecule Junctions Formed by Mechanically Controllable Break Junctions with Side Gating

Molecules are promising candidates for electronic device components because of their small size, chemical tunability, and ability to self-assemble. A major challenge when building molecule-based electronic devices is forming reliable molecular junctions and controlling the electrical current through the junctions. Here, we report a three-terminal junction that combines both the ability to form a stable single-molecule junction via the mechanically controllable break junction (MCBJ) technique and the ability to shift the energy levels of the molecule by gating. Using a noncontact side-gate electrode located a few nanometers away from the molecular junction, the conductance of the molecule could be dramatically modulated because the electrical field applied to the molecular junction from the side gate changed the molecular electronic structure, as confirmed by the ab initio calculations. Our study will provide a new design for mechanically stable single-molecule transistor junctions fabricated by the MCBJ method.

Electrostatic tailoring of magnetic interference in quantum point contact ballistic Josephson junctions

The magnetoelectrostatic tailoring of the supercurrent in quantum point contact ballistic Josephson junctions is demonstrated. An etched InAs-based heterostructure is laterally contacted to superconducting niobium leads, and the existence of two etched side gates permits, in combination with the application of a perpendicular magnetic field, continuous modification of the magnetic interference pattern by depleting the weak link. For wider junctions the supercurrent presents a Fraunhofer-like interference pattern with periodicity $h/2e$, whereas by shrinking electrostatically the weak link, the periodicity evolves continuously to a monotonic decay. These devices represent tunable structures that might lead to the study of the elusive Majorana fermions.

Improving Warpage on Thin Shallow Parts in Two-Plate Moulds with Conformal Cooling Channels

Nowadays, the trend of consumer products designed is getting smaller and most of cover is made from plastic which was produced by using injection molding process. Thus, the demand of thin shallow plastic parts in global industries is increasing today. In addition, manufacturing engineers have difficulties to control the parameters during processing the 1 mm thickness of the thin shallow parts where the warpage defect is the common issue especially for the thin parts. Therefore this study is performed purposely to evaluate the performance of conformal cooling channels compared to the straight drilled cooling channels in order to minimize the warpage on the thin shallow parts. The type of gating systems used in this study is side gate, which is commonly gate in 2-plate mold. The results from simulation through Autodesk Moldflow Insight (AMI) 2013 are analyzed by using Taguchi Method and Analysis of Variance (ANOVA). Results from this study show that conformal cooling channels are able to improve the quality of the molded parts in term of warpage compared to the conventional straight drilled cooling channels. This is beneficial for the molding industries especially for the precise parts.

3차원 EFDC-WASP 연계모델을 이용한 경인아라뱃길 수질 예측

Ara Canal is the first artificial canal in Korea that connects the Han River and the Yellow Sea. Due to mixture of waters with different salinity and water quality, complicated hydrodynamic and water quality distributions are expected to occur inside the canal. An integrated hydrodynamic and water quality modeling system was developed using the 3 dimensional hydrodynamic model, EFDC (Environmental Fluid Dynamics Code) and the water quality model WASP (Water Quality Analysis and Simulation Program). According to the modeling results, BOD, TN, TP and Chl-a concentrations inside the canal were lower at the West Gate side than the Han River side since influent concentrations of the West Gate side are significantly lower. Chemical stratification due to salinity difference were more evident at the West Gate side as vertical salinity difference were more pronounced in this area. On the other hand, Chl-a concentrations showed more pronounced vertical distribution at the Han River side as Chl-a concentrations were higher in this area. It was notable that Dissolved Oxygen concentrations can be lower than 2 mg/L occasionally in the middle part of the canal. While major factor affecting DO concentrations in the canal are inflows via both gates, the other important factor was found to be BOD decay in the canal due to extended hydraulic residence time. This study can be used to predict hydrodynamic conditions and water quality in the canal during the year and thus can be helpful in the development of gate operation method of the canal.

Intrinsic bistability in quantum point contacts with in-plane side gates

We study the onset of intrinsic bistability and accompanying hysteresis in a single quantum point contact (QPC) with in-plane side gates in the presence of lateral spin-orbit coupling. The hysteresis in the conductance versus common gate voltage applied to the two side gates exists only if the narrow portion of the QPC is long enough. The hysteresis is absent if the effects of electron-electron interaction are neglected but increases with the strength of the electron-electron interaction. The hysteresis appears in the region of conductance anomalies, i.e., less than 2e2/h, and is due to multistable spin textures in these regions.

Analysis of the residual stress distribution in AlGaN/GaN high electron mobility transistors

A comparative analysis of the residual stress distributions across the conductive channel of Ga-face AlGaN/GaN high electron mobility transistors (HEMTs) is presented. Stress was measured by means of micro-Raman spectroscopy and micro-photoluminescence (PL). Raman measurements probed the volume average of the stress through the GaN layer whereas the stress near the GaN surface (AlGaN/GaN heterointerface) was acquired via PL. By combining Raman, PL, and x-ray diffraction, a self-consistent method was developed to accurately determine the variation in magnitude of stress throughout the thickness of the GaN layer. Based on this framework, it is observed in AlGaN/GaN HEMTs that a depth variation in the GaN residual stress occurs near the gate and ohmic electrodes. At these regions, the stress near the AlGaN/GaN interface (or GaN surface) exhibits a tensile shift compared to the stress averaged through the entire thickness of GaN. Across the conductive channel (away from the metal pads), the bulk average stress and the stress near this interface remain nearly identical, showing little evidence of a vertical gradient. It is expected that the induced tensile strain at the drain side gate edge will have an impact on device reliability by contributing to the elastic energy built in the AlGaN barrier in addition to the inverse piezoelectric contribution at operating conditions, which may lead to formation of crystallographic defects.