Micro and Nanostructures最新文献

To avoid Shockley-Queisser limit in single p-n junctions, tandem solar cells were proposed. A new tandem cell is simulated here using the 1-dimensional SCAPS. The new cell combines two reported single solar cells together, aiming at achieving high performance by optimizing various layer characteristics. The bottom sub-cell is Mo/Si(p)/CZTSSe(p)/CdS(n)/ZnO(i)/ZnO(Al), where ZnO is an electrodeposited transparent-conductor oxide, with high UV transmittance, ZnO(i) is intrinsic layer, CZTSSe/Si is bi-absorber layer of p-CuZnSnSSe and p-Si, Mo is back contact. The optimized sub-cell exhibits a high fill factor of 85.18 % with overall efficiency 20 %. Based on literature, a perovskite CsPbI₂Br layer is included in the top sub-cell Cu₂O(HTL)/CsPbI₂Br)/TiO₂(ETL), where Cu₂O is a hole-transport layer and TiO₂ is electron-transport layer. The top sub-cell layers have been carefully selected for best alignment. Matching and optimizing various parameters in the two sub-cells is a simulation challenge. Therefore, layers in the two sub-cells have been studied separately, keeping in mind the proper combinations between various layers. With optimized layer thicknesses and band gaps, together with proper alignment of band edges, the proposed tandem solar cell exhibits high characteristics of 80 % fill factor and higher than 32 % overall efficiency.

Owing to the fact that the gate-all-around architecture is expected to prevail in the upcoming technology nodes, in this work we have taken up a simulation-based investigation on design of a gate-all-around junctionless transistor (GAA-JLT) based label-free gas sensor with conducting polymer (CP) gate. In the initial part of our work we have focused on the variation n device and sensor performance with initial work function of the CP, which depends upon its growth condition and primary doping. Interaction with various test gases modifies the CP characteristics, thereby changing its work function. Due to this a change in device characteristics is observed, which serves as the metric for assessing the GAA-JLT-based gas sensor performance. We have investigated the variation in device characteristics in the presence of different test gases. Further, the variation in sensor performance on interaction with the different test gases has been examined. The impact of operating conditions such as ambient temperature and partial pressure of the test gas on the sensing performance has been investigated. The impact of device dimension on the sensing performance has also been evaluated. Our computations reflect that tuning the initial work function of the CP by choosing the proper primary dopant concentration model along with proper tuning of the operating conditions can enhance the performance accuracy of the sensor.

This paper proposes an equivalent circuit model for two-line coupled multilayer graphene nanoribbon - single-wall carbon nanotube (MLGNR-SWCNT) composite interconnects (MSCs), incorporating the effects of coupling capacitance and mutual inductance. We also examine the temperature-dependent crosstalk effect on the victim line of MSCs in the time domain using decoupling techniques and the ABCD parameter matrix approach. This analysis is conducted at the global level of 7 nm, 14 nm, and 22 nm technology nodes, comparing the performance of MSCs with MLGNR, SWCNT, and copper (Cu) interconnects, validated through HSPICE simulations. Our results reveal that the crosstalk delay of all interconnects induced by dynamic crosstalk exhibits superior performance in the in-phase crosstalk mode compared to the out-of-phase mode at room temperature. In particular, MSCs demonstrate less crosstalk delay in both crosstalk modes compared to SWCNT and Cu interconnects. In addition, we analyze the crosstalk delay of the victim line for two-line coupled MSCs at varying temperatures in out-of-phase crosstalk mode, comparing them with MLGNR, SWCNT, and Cu interconnects. Simulation results indicate that the crosstalk delay is temperature-dependent, increasing with rising temperatures, and the crosstalk delay of MSCs is the least of all interconnects. Furthermore, we investigate the crosstalk noise of MSCs induced by functional crosstalk at different temperatures, comparing it with MLGNR, SWCNT, and Cu interconnects. It is observed that the crosstalk noise peak remains constant with temperature changes across all interconnects; however, the holding time and width of crosstalk noise increases with rising temperatures and MSCs have the least crosstalk noise peak and crosstalk noise width of all interconnects. Also, numerical results exhibit that reducing interconnect temperature, SWCNT diameter, and edge roughness of MLGNR are effective strategies to diminish the crosstalk delay of MSCs. In addition, increasing line spacing is identified as an effective method to reduce crosstalk noise peak of MSCs of different lengths. The proposed model results show excellent agreement with HSPICE simulation data. Therefore, our analysis of crosstalk effect manifests that MLGNR-SWCNT composite can be a promising material to replace SWCNT and copper as an ideal material for global interconnect applications in thermally variable environments.

The influence of the annealing treatment on the performance of commercial 4H–SiC Schottky barrier diodes (SBDs) subjected to heavy ion irradiation under room temperature (RT) and low temperature (LT) are presented. Experimental results confirm that annealing treatment effectively eliminates defects and interface states caused by heavy ion irradiation, particularly for 4H–SiC SBD under LT irradiation. Increasing the annealing temperature leads to the slight improvement in forward current, leakage current and breakdown voltage. However, the annealing process may result in the formation of Ti and Si compounds at the interface between the Schottky metal and SiC, as well as a significant number of vacancies. Combined with Technology Computer Aided Design (TCAD) simulations, it is concluded that the interface trap charge concentrations exceeding 1 × 10¹² cm⁻² significantly impact the breakdown characteristics of 4H–SiC SBDs.

This work presents the comparative study of Graphene Nanoribbon (GNR) based channel Double Gate (DG) Dual Gate Material (DMG) Vertical tunnel Field Effect Transistor (VTFET) performance with all Silicon material Tunnel Field Effect Transistor. The two-dimensional (2D) material GNR has been proposed in the channel material to enhance the device performance due to its low bandgap, high mobility, and high saturation velocity. The proposed device's DC, RF, and circuit-level performance analysis has been carried out for the first time. GNR-based channel VTFET shows a better average subthreshold swing (SS_AVG) of 16 mV/decade compared to Silicon Vertical Tunnel FET (36 mV/decade) at a drain voltage V_DS = 0.5 V. The study of temperature effects on the DC parameters is also included along with the analog/RF FOMs for the proposed two structures. In addition, the performances are compared with other reported works; it is observed that DG-GNR-DMG-VTFET offers better results than Silicon (Si)-based VTFET and other said TFET work. Finally, circuit-level analysis has been done by designing inverter and ring oscillator circuits for the proposed structures, and performance is compared in these two devices. The market-available Silvaco ATLAS TCAD simulator has been used for device-level simulation. Further, circuit-level analysis has been carried out in the Cadence Virtuoso tool using a look-up table-based Verilog-A model.

Wireless energy harvesting is an important application of microwave wireless energy transmission system, but due to the weak energy of RF signals in the 2.45 GHz band, its rectification efficiency is not ideal. As one of the core rectifier components of wireless weak energy harvesting system, the performance of MOSFET determines the rectification efficiency of the system, and its optimized design to improve the rectification efficiency is an important direction of current research in the field. In view of this, this paper proposes and designs Ge quantum well channel PMOS for wireless weak energy harvesting at 2.45 GHz, aiming to improve the rectification efficiency of wireless weak energy harvesting systems. Starting from adjusting the structural physical parameters of the MOS tubes, the absolute value of the threshold voltage is reduced in the weak energy density region, which in turn improves the rectification efficiency of the device. Then, the novel diode connection with the introduction of substrate bias effect is compared with the conventional connection using an ADS simulation circuit, and the simulation results show that the leakage current is smaller and the rectification efficiency is higher under the novel connection. On this basis, a Ge quantum well channel PMOS device is proposed. Compared with the Ge surface channel, the hole mobility of the quantum well channel will be greatly improved, and its rectification efficiency can also be improved. The device is connected to the rectifier circuit with a novel connection and simulated using Silvaco's Mixedmode module. The results show that the rectification efficiencies of the Ge quantum well channel MOS reach 13.53 % and 32 % at low input powers of −20.34 dBm and −6.28 dBm, respectively, which are 3.3 and 1.14 times higher than those of the conventional surface channel MOS.

In this paper, a bi-tunable metamaterial absorber comprising a subwavelength resonator of semiconducting material InAs and a metallic plane adhered to a dielectric layer has been proposed in the terahertz regime. Absorption of about 99.8 % is achieved at 4.446 THz with the application of magnetic field B = 0.4 T and a high tunability rate of 0.4 THz/T in the central resonance frequency due to the presence of a magnetostatically tunable H-shaped InAs resonator and polyimide dielectric layer. The same structure supports dual control over the resonance by replacing polyimide dielectric layer with InSb, as InSb possesses temperature- and magnetic field-dependent dielectric properties. The replacement of polyimide dielectric layer with InSb provides near unity absorption of 99.99 % at B = 0.4 T but when the effect of temperature on the absorption is taken, it provides a high absorptivity of 99.99 % at T = 285 K with a blue shift in the maximum resonance frequency, providing tunability of 0.016 THz/K on increasing the temperature from 280 K to 295 K. Thus, the proposed absorber not only provides dual control over the resonance spectrum but also progresses towards more practical applications in the sensing and detection of temperature variance.

In order to effectively regulate the luminescence performance of MQW and enhance its optical quality, it is crucial to investigate the InGaN/GaN MQW's structure and luminescence properties. In this study the focus is how they are affected by low-temperature cap (LT-cap) layer's thickness which is grown above each InGaN well layer during growth process of InGaN/GaN multiple quantum well (MQW) samples in MOCVD system. This was achieved by analyzing high resolution X-ray diffraction (HRXRD) spectra, electroluminescence (EL) spectra, temperature-dependent photoluminescence (TDPL) spectra, and micro-area fluorescence imaging of these samples. The results show that changes in LT-cap layer's thickness even have no significant impact on some structural parameters of MQW, such as the thickness of the well layer, but have an influence on the In component of the well layer. Due to the existence of LT-cap layer, dissociation of InGaN can be effectually reduced. In addition, the augmentation of LT-cap layer's thickness will make polarization effect of the QW sample more remarkable, so that the blue shift of the EL peak with the augmentation of current injection increases. The change of LT-cap layer's thickness will also influence distribution of the tail states of the quantum wells, which leads to a different localization states for injected carriers. As LT-cap layer becomes getting thicker, the material's internal quantum efficiency (IQE) tends to decrease, which may result from an increase in non-radiative recombination centers.

The strong coherent coupling in different electromagnetic modes can control the light-matter interaction more conveniently. Here, we theoretically researched the hybridization between the borophene surface plasmon (BSP) mode and the borophene localized surface plasmon (BLSP) mode in borophene grating structure. This coupling effect leads to the emergence of multiple hybrid modes. The absorption spectra of the system are investigated through finite difference time domain (FDTD) simulation and coupled oscillator model (COM). Results show that the coherent coupling of BSP and BLSP can be achieved by adjusting the carrier density of the borophene gratings. A Rabi splitting effect with frequency of 21.6 THz can be observed. Furthermore, we investigated the effects of geometric structural parameters, incident angle, and relaxation time on the correlated coupling spectra. Our work may deepen the understanding of light–matter interactions and provide a reference for borophene-based active photonic devices in the near-infrared region.

This research work evaluates a performance analysis of heterostructure (SiGe/Si) double gate extended source Tunnel FET (Hetero-ES-TFET) to enhance the analog performance, linearity and noise performance. At the source-channel junction, a Hetero-ES-TFET's source is extended into the channel to increase point and line tunneling in the device. The Hetero-ES-TFET exhibits a high I_ON/I_OFF of 3.57 × 10¹² and a maximum cut off frequency f_T of 54.19 GHz for optimization of device structural parameters. This analysis is conducted using a calibrated SILVACO, technology computer-aided design (TCAD) simulator. The proposed structure includes evaluation of linearity and noise performance characteristics. Furthermore, a linearity analysis as a figure of merit was conducted for the proposed device under study, including different parameters such as 3^rd order intermodulation distortion point (IMD₃), 3^rd order intermodulation intercept point (IIP₃), 2^nd and 3^rd order voltage intercept point (VIP₂ and VIP₃). The proposed Hetero-ES-TFET has achieved an incredibly high ON current and low threshold voltage. The effect of increasing source width has been examined in this work while sub-threshold swing (SS) remains unchanged during the analysis. There is an improvement in threshold voltage and I_ON/I_OFF value by using silicon-germanium (SiGe) as a source material.