An inserted novel polarization-graded AlGaN back barrier structure is designed to enhance performances of In_0.17Al_0.83N/GaN high electron mobility transistor (HEMT), which is investigated by the two-dimensional drift-diffusion simulations. The results indicate that carrier confinement of the graded AlGaN back-barrier HEMT is significantly improved due to the conduction band discontinuity of about 0.46 eV at interface of GaN/AlGaN heterojunction. Meanwhile, the two-dimensional electron gas (2DEG) concentration of parasitic electron channel can be reduced by a gradient Al composition that leads to the complete lattice relaxation without piezoelectric polarization, which is compared with the conventional Al_0.1Ga_0.9N back-barrier HEMT. Furthermore, compared to the conventional back-barrier HEMT with a fixed Al-content, a higher transconductance, a higher current and a better radio-frequency performance can be created by a graded AlGaN back barrier.

This paper presents a high quality-factor (Q) and spectrum-clean AlN Lamb-wave resonator (LWR). The width of its lateral reflection boundary was optimized to weaken the transverse modes’ coupling and wave guiding, and then to improve the LWR’s Q value and spectral purity, which was verified by finite element analysis and experimental characterization. In addition, the series resonance quality factor (Q_s) value of the interdigitated (IDT)-Ground LWR is similar to that of the IDT-Floating LWR, but its parallel resonance quality factor (Q_p) is nearly doubled, due to the reduction of the electrical loss induced by its static capacitance (C₀). The measured results show that the designed LWR with optimized boundary reflection conditions and IDT-Ground structure exhibit Q_s and Q_p values as high as 4019.8 and 839.5 at 401.2 MHz and 402.9 MHz, respectively, meanwhile, it has good spectral purity. Moreover, the influence of the metal ratio and material of the LWR’s IDT electrodes on the device’s performance was also studied by theoretical analysis and experimental verification.

This paper numerically investigates the effects of airfoil leading edge radius on the aerodynamic characteristics of H-rotor Darrieus vertical axis wind turbine (VAWT). 10 modified airfoils are generated by changing the leading edge radius of the base NACA 0015 airfoil from 1%c to 9%c, respectively. A 2D unsteady Computational Fluid Dynamics (CFD) model is established and validated with the previously published experimental data. The power, torque, and flow field characteristics of the rotors are analyzed. The results indicate that the maximum and minimum power coefficient at the optimum tip speed ratio (TSR) are obtained for the LE-5%c and LE-1%c model, respectively. The best aerodynamic characteristics are determined by the LE-5%c model below the optimum TSR and the LE-3%c model beyond the optimum TSR. The torque characteristics and pressure distribution for the single blades with different airfoil leading edge radius show an obvious difference in the upwind region and a very small difference in the downwind region. Moreover, the airfoil leading edge radius influences the strength, region, and diffusion rate of the vortices, being the main reason for the observed differences in instantaneous torque coefficient and power coefficient. The vortices of the LE-1%c model are stronger, larger, and diffuse slower than those of the LE-2%c and LE-5%c model at the optimum TSR.

This work reports a batch fabrication process for silicon nanometer tip based on isotropic inductively coupled plasma (ICP) etching technology. The silicon tips with nanometer apex and small surface roughness are produced at wafer-level with good etching homogeneity and repeatability. An ICP etching routine is developed to make silicon tips with apex radius less than 5 nm, aspect ratio greater than 5 at a tip height of 200 nm, and tip height more than 10 μm, and high fabrication yield is achieved by mask compensation and precisely controlling lateral etch depth, which is significant for large-scale manufacturing.

A chiplet multi-objective optimization algorithm for 2.5-D integrated circuit (IC) based on a passive interposer is discussed in this article. Inspired by the network-on-chip mapping problem, we propose a novel algorithm, called chiplet multi-objective optimization, which minimizes the average temperature and the communication consumption between chiplets at the same time. The algorithm considers the specificities of 2.5-D IC chiplets, such as the spacing and different sizes of chiplets. In addition to the weight factor, α is also introduced to make a balance between temperature and the communication consumption. The designer can change the weight factor according to their own requirement. The multi-window display system is used as an example in this article to demonstrate the algorithm’s efficiency and the accuracy. According to our algorithm, the system temperature of the most ideal solution can be reduced by 8.34 K and the communication consumption reduced by 232.13 μJ.

In this work, a novel design scheme for a high-performance surface acoustic wave (SAW) filter with dual acoustic mode hybrid integration is proposed. Based on X-cut LiNbO₃/SiO₂/SiC (LNOSiC) hetero-substrate, the dual-mode ladder-type filter employs the high-electromechanical-coupling shear horizontal (SH) mode as the main mode for parallel resonators and high-power longitudinal leaky (LL) mode for series resonators, respectively. The fabricated hybrid dual-mode filter aiming at the n79 band shows a large 3-dB fractional bandwidth (FBW) ${}_{\mathrm {3dB}}$ ) of 12.4%, a low insertion loss (IL) of 1.05 dB, high peak power handling of 29 dBm, and a high out-of-band (OoB) rejection of 38 dB over a wide frequency range. Low-loss SH-SAW and LL-SAW filters are also fabricated for comparative analysis. The hybrid filter demonstrates an FBW ${}_{\mathrm {3dB}}~1.3$ times larger than the LL-SAW filter, with a P1dB power handling nearly 2.5 times that of SH-SAW filters. These results demonstrate the comprehensive performance advantages of the proposed dual-mode filter technology as well as its strong potential for advanced 5G communication systems.