Micro and Nanostructures最新文献

The fabrication complexity, low sensitivity, detection speed, and costs associated with nanoscale devices have been significant concerns in the development of label-free biosensors. To address these issues, we report a novel dual material control gate cavity on source electrically doped tunnel field-effect transistor (DM-CG-CS-ED-TFET) for label-free biosensors. In this regard, the n⁺ drain and p⁺ source regions within the proposed device are induced by applying polarity gate (PG) bias voltages of PG-1 = +1.2 V and PG-2 = −1.2 V, respectively, across the respective polarity gate electrodes. This approach not only overcomes doping control issues but also avoids thermal budget constraints and minimizes fabrication complexity when compared to conventional TFET. For biomolecule sensing in the device, a nanogap cavity is created within the gate dielectric by selectively etching a portion of the polarity gate dielectric layer towards the source side. The performance of the proposed biosensor device is evaluated based on the variations in carrier concentration profile, energy band diagram, electric field, transfer (I_DS - V_GS) characteristics, drain current (I_DS) sensitivity, ON-state current (I_ON) sensitivity, switching ratio (I_ON/I_OFF) and subthreshold swing (SS) sensitivity. The sensitivity of the device is also investigated based on nano-cavity dimensions, practical challenges such as various filling factors, and the step profile generated from the steric hindrance. Moreover, the effect of temperature on sensitivity has also been investigated. For this, various biomolecules including Streptavidin (k = 2.1), APTES (k = 3.57), ferrocytochrome c (k = 4.7), keratin (k = 8) and Gelatin (k = 12), have been investigated for their performance using Silvaco ATLAS device simulator. The simulation results demonstrate that the proposed biosensor is a viable option for biosensing applications in biomedical engineering.

In this study, an AlGaN/GaN high electron mobility transistor with lateral inhomogeneous AlGaN barrier layer (LI-AlGaN HEMT) is proposed and studied systematically. The LI-AlGaN HEMT comprises three AlGaN regions with varying Al content, connected to the source, gate, and drain, respectively. With the increase of Al content in each region, the saturation current of the LI-AlGaN HEMT increases gradually, while the on-resistance (R_on) and breakdown voltage (BV) decrease. The threshold voltage (V_th) of the LI-AlGaN HEMT depends only on the Al content of AlGaN beneath the gate. By introducing the source field plate (FP), the calculated output current of the conventional FP-HEMT is consistent with the experimental data. After optimizing Al content, the LI-AlGaN FP-HEMT has the same V_th compared with conventional FP-HEMT. However, the saturation current is increased by approximately 20 % and the R_on is decreased by approximately 30 %. Additionally, the BV is increased to 1008 V. So the optimized lateral inhomogeneous AlGaN HEMT has better DC characteristics and is suitable for high power GaN device applications.

In this work, a novel bio-inspired artificial gustatory system is proposed for in-sensor neuromorphic computing. The system is demonstrated using a novel material-engineered compound-semiconductor double-gate ferroelectric tunnel FET. The behaviour of the device as a biosensor and as a spiking neuron is verified individually. Using extensive simulation in Atlas TCAD, the biosensor functionality is validated with I_ON sensitivity of 10⁸. Likewise, the device shows excellent neuronal behaviour with energy consumption of 37 aJ/spike, without using any external circuitry. It also exhibits control over the spiking frequency through amplitude, frequency, and duty cycle of input synaptic current. By cascading the biosensor and neuron, a complete bio-mimicked gustatory system is designed to identify a separate pattern for different tastes. The proposed gustatory system integrates both the devices, and simultaneously performs sensing and spike encoding. The biosensor transduces the pH and dielectric constant of the target biomolecule, corresponding to gustatory neurons present in the taste buds of a biological gustatory system. The neuron performs spike encoding and acts as an input neuron in a classifying network, which corresponds to gustatory cortex of its biological counterpart. The system consumes an average power of 49.58 pW which is ∼1000 × lesser than the state-of-the-art artificial gustatory system, eliminating the need for complex hardware and exorbitant energy consumption. Therefore, the proposed gustatory system provides a highly efficient and compact solution for neuromorphic gustatory sensing and classification, with potential applications in portable, wearable, and implantable devices.

This piece of work highlights the application of dual-metal double-gate VTFET as label free biosensor having enhanced switching ratio, current driving capability and sub-threshold swing and consequently high sensitivity. The use of dual-material namely tunneling gate and auxiliary gate in this device leads to high switching ratio (I_ON/I_OFF) and low sub-threshold swing (SS). In order to observe outcome of this suggested biosensor, various biomolecules dielectric constant have been considered and examined with respect to electric field, energy band diagram, drain current characteristics and sub-threshold potential profile. Neutral biomolecules with a higher dielectric constant exhibits greater drain current sensitivity against biomolecules having lower dielectric constant. Here effect of cavity interface charge on the sensitivity performance of the proposed biosensor device is also verified. This fabrication feasible homo vertical TFET based biosensor gives best sensitivity performance for K = 12, both for the current (5.44 × 10⁵) and transconductance (3.14 × 10⁵) with the minimal sub-threshold swing of 9.9 mV/decade. Silvaco, a commercially accessible TCAD tool is used to investigate the proposed structure.

In this paper, a deep ultraviolet light-emitting diode (DUV LED) at ∼275 nm with an interval-graded barrier superlattice (IBSL) Electron Blocking Layer (EBL) has been proposed and numerically investigated. The IBSL EBL structure has greatly increased the carrier concentration within the active region. It has been shown that DUV LEDs with IBSL EBL structure exhibits transcendent electron blocking and hole injection capabilities compared to conventional DUV LEDs, which is attributed to the increased lattice matching and decreased polarization effects brought about by the smaller Al content difference between the superlattice barriers and wells. Consequently, compared to the conventional DUV LEDs at a 60 mA injection current, the internal quantum efficiency and the light output power of DUV LEDs with IBSL EBL have been enhanced by 34 % and 30 %, respectively.

We investigate the optoelectronic spin and spin-valley transports and magnetoresistance (MR) effect in a graphene-based junction. The results show that by modulating the direction of an electric field, the off state and the on state with fully spin-polarized currents can be realized for both parallel (P) and antiparallel (AP) magnetization configurations, because the spin-polarized directions between two antiferromagnetic (AFM) regions are opposite and consistent, respectively. Moreover, when the off-resonant circularly polarized (ORCP) light is further radiated on two AFM regions, pure spin current can be further switched into four types of fully spin-valley-polarized currents, which results in an optoelectronically controlled transistor. In particular, the conductances in the P and AP magnetization configurations are either equal or dramatically different, so the optically and electrically controlled MR effect is naturally formed that can be switched from 0 to 1. Our results suggest that graphene has a very promising potential for applications in spintronics and spin-valleytronics.

This study focuses on the physical exploration, particularly examining the structural and electrical attributes of ZnO thin films produced through spray deposition, with variations in the Ni/Zn ratio (0.25 %, 0.5 %, and 0.75 %). X-ray diffraction (XRD) analysis reveals that both undoped and Ni-doped ZnO films exhibit a hexagonal crystalline structure, with a preferred orientation along the (002) direction perpendicular to the substrate. The semiconductor nature of all prepared compounds is confirmed by the grain boundary resistance. An escalation in Ni concentration corresponds to an increase in grain boundary resistance. The activation energy values, derived from both relaxation time and grain boundary resistances, closely align. Impedance studies indicate the presence of two relaxation processes within the compounds. The Nyquist diagram illustrates the emergence of semicircles, with decreasing radii at higher temperatures, indicating thermally activated semiconductor behavior in these samples, as evidenced by electrical conductance and distribution of relaxation times.

Due to its versatility, metal oxide semiconductor field effect transistor (MOSFET) based devices are seeing tremendous growth in demand. To meet the demands of high speed and low power consumption, these MOS devices are continually scaling down to produce next-generation hardware. But the shot channel effects and the limitation in the minimum subthreshold swing (SS > 60 mV/Dec), stop the further scaling of the MOSFET device. The Tunnel FET (TFET) is considered as a suitable potential replacement for the MOSFET due to its unique band-to-band tunneling (BTBT) charge carrier transport and superior subthreshold characteristics (SS < 60 mV/Dec). The TFET device effectively eliminates the SCE and allows the fine scaling of the device required by the industry. However, the TFET suffers from low ON(I_ON) current and ambipolar conduction, which makes the performance hectic for the TFET device. So, researchers proposed various methods to overcome these challenges, and gate structural engineering (GSE) and gate work function engineering (GWE) are the most recommended and yield good results for TFET. In this review paper, we have performed a comparative investigation on different devices reported on these two techniques by taking various parameters of the TFET. A detailed analysis is carried out to reveal how these techniques enhance the on (Ion) current and suppress the ambipolar current of the device. Especially the impact of the change in gate structure and gate metal work function on the tunneling width of the device focused by considering the device's electrostatic. A comparative study of different TFET architectures with different electrical parameters is reported.

In this article, we proposed a core-shell (CS) architecture that uses the silicon carbide (SiC) as a nanowire for higher breakdown voltages in a Junctionless field effect transistor (JLFET). The P⁺ core-shell improves the electrostatic integrity and reduces lateral band-to-band tunneling in SiC JLFET. Furthermore, the SiC is wide band gap material which helps to achieve the full volume depletion in JLFET at such short channel lengths. Thus, the OFF-state current in P⁺ SiC CS JLFET has reduced to 10⁻¹⁶ μA even at temperature 600 K and V_DS = 2.0 V. The P⁺ SiC CS JLFET shows significant performance even at higher drain voltages. Hence, we investigate the P⁺ SiC CS JLFET for higher breakdown voltages with the impact of higher temperatures. In addition, the impact of higher drain voltages with higher temperatures is also examined. This paper presents an analytical model for P⁺ SiC CS JLFETs which considers Poisson's equation for nanowires as well as the surface potential at the threshold voltage (V_th) and electric field at the zero point (E_z). The model shows that the surface potential and the electric fields in nanowires are essential for an accurate estimation of the drain current. In addition to the numerical modeling results provided by SILVACO TCAD, the performance of the proposed analytical model was compared with simulation results. The results showed good agreement between the simulations and the proposed compact model. This indicates that the proposed model can be used to provide accurate drain current predictions in nanoscale transistors.

Indium arsenide (InAs) nanowires (NWs) show significant advantages in optoelectronic devices due to their excellent electronic and optical properties. While the surface states affect such outstanding properties, and the performance of optoelectronic devices can be further optimized by modulating the surface state. Herein, the adsorption and substitution properties and the optoelectronics response of passivated InAs NWs are studied using first-principles calculations combined with nonequilibrium Green's function (NEGF). The results show that O atom adsorption can reduce the band gap and improve infrared absorption of InAs NWs. Meanwhile, for the O atom substitution model, the impurity energy level appears near the Fermi level of InAs NWs, and for a higher concentration O atoms substitution, the semiconduction properties of the InAs NWs are destroyed. We also choose the Au, Cs, Bi, Sn, and Y atoms as decoration atoms to passivate InAs NWs, and compared with the intrinsic InAs NW surface model, the energy bands gap of the metal-atoms adsorption models all show a decreasing trend in addition to Au-atom adsorption, and the absorption coefficients of InAs NWs adsorbed by several atoms such as Cs, Sn, Bi, and Y in the infrared region have redshifts in different degrees. The absorption coefficients of InAs NWs adsorbed by several metal atoms, Sn, Bi, and Y, are higher in the infrared region compared to that of InAs NW adsorbed by O atom. After the screening of materials, we select InAs NWs adsorbed with Cs, Bi, Sn, and Y atoms with good infrared absorption characteristics for the performance study of optoelectronic devices and it is shown that the InAs NW devices with adsorbed Bi and Sn atoms have the optimal performance with low dark current and high photocurrent.