The terminal structure of the PiN diode has undergone several improvements since its development. The field-limiting ring (FLR), junction termination extension (JTE), Mesa technology (Mesa), and composite terminal technologies are the leading technologies for modifying this terminal structure. For example, Sheridan et al. studied the breakdown characteristics of SiC-PiN diodes with single- and multi-region JTE terminal structures in 2001. In 2005, Perez et al. conducted a comparative study of various planar terminal technologies, mainly JTE terminals, FLR terminals, and their composite structures based on a 1.7 kV SiC-PiN diode. Field-ring-assisted junction extension terminals (GA-JTE) can effectively increase the breakdown voltage for devices with lower JTE concentration and broaden the range of JTE optimal values. In 2009, Ghandi et al. from the Royal Institute of Technology, Sweden, successfully developed a high-voltage SiC-PiN diode with a dual-zone etch JTE terminal. The breakdown voltage of the device was measured as 4.3 kV. Niwa et al. used a space-modulated junction termination extension (SM-JTE) terminal to broaden the JTE optimal concentration window to avoid the influence of the interface charge. Salemi et al. developed a breakdown voltage for a SiC bipolar transistor with a four-stage etched JTE terminal reaching 15.8 kV at the Royal Institute of Technology, Sweden, in 2018. This study thoroughly reviewed the effects of 4H SiC-PiN diode terminal structures on the breakdown voltage.

In recent years, the treatment of agricultural wastewater has been an important aspect of environmental protection. The purpose of photocatalytic technology is to degrade pollutants by utilizing solar light energy to stimulate the migration of photocarriers to the surface of photocatalysts and occur reduction-oxidation reaction with pollutants in agricultural wastewater. Photocatalytic technology has the characteristics of high efficiency, sustainability, low-energy and free secondary pollution. It is an environmental and economical method to recover water quality that only needs sunlight. In this paper, the photocatalysis process is combined with agricultural treatment technology to summarize a review of photocatalytic removal of heavy metal ions and antibiotics from agricultural water pollution, and the factors affecting photocatalytic degradation technology.

Waveguide-integrated optical modulators are indispensable for on-chip optical interconnects and optical computing. To cope with the ever-increasing amount of data being generated and consumed, ultrafast waveguide-integrated optical modulators with low energy consumption are highly demanded. In recent years, two-dimensional (2D) materials have attracted a lot of attention and have provided tremendous opportunities for the development of high-performance waveguide-integrated optical modulators because of their extraordinary optoelectronic properties and versatile compatibility. This paper reviews the state-of-the-art waveguide-integrated optical modulators with 2D materials, providing researchers with the developing trends in the field and allowing them to identify existing challenges and promising potential solutions. First, the concept and fundamental mechanisms of optical modulation with 2D materials are summarized. Second, a review of waveguide-integrated optical modulators employing electro-optic, all-optic, and thermo-optic effects is provided. Finally, the challenges and perspectives of waveguide-integrated modulators with 2D materials are discussed.

Fifteen periods of Si/Si_0.7Ge_0.3 multilayers (MLs) with various SiGe thicknesses are grown on a 200 mm Si substrate using reduced pressure chemical vapor deposition (RPCVD). Several methods were utilized to characterize and analyze the ML structures. The HRTEM results show that the ML structure with 20 nm Si_0.7Ge_0.3 features the best crystal quality and no defects are observed. Stacked Si_0.7Ge_0.3 ML structures etched by three different methods were carried out and compared, and the results show that they have different selectivities and morphologies. In this work, the fabrication process influences on Si/SiGe MLs are studied and there are no significant effects on the Si layers, which are the channels in lateral gate all around field effect transistor (L-GAAFET) devices. For vertically-stacked DRAM (VS-DRAM), it is necessary to consider the dislocation caused by strain accumulation and stress release after the number of stacked layers exceeds the critical thickness. These results pave the way for the manufacture of high-performance multivertical-stacked Si nanowires, nanosheet L-GAAFETs, and DRAM devices.

Two-dimensional (2D) antiferroelectric materials have raised great research interest over the last decade. Here, we reveal a type of 2D antiferroelectric (AFE) crystal where the AFE polarization direction can be switched by a certain degree in the 2D plane. Such 2D functional materials are realized by stacking the exfoliated wurtzite (wz) monolayers with “self-healable” nature, which host strongly coupled ferroelasticity/antiferroelectricity and benign stability. The AFE candidates, i.e., ZnX and CdX (X=S, Se, Te), are all semiconductors with direct bandgap at Γ point, which harbors switchable antiferroelectricity and ferroelasticity with low transition barriers, hidden spin polarization, as well as giant in-plane negative Poisson’s ratio (NPR), enabling the co-tunability of hidden spin characteristics and auxetic magnitudes via AFE switching. The 2D AFE wz crystals provide a platform to probe the interplay of 2D antiferroelectricity, ferroelasticity, NPR, and spin effects, shedding new light on the rich physics and device design in wz semiconductors.

Metallic few-layered 1T phase vanadium disulfide nanosheets have been employed for boosting sodium ion batteries. It can deliver a capacity of 241 mAh g⁻¹ at 100 mA g⁻¹ after 200 cycles. Such long-term stability is attributed to the facile ion diffusion and electron transport resulting from the well-designed two-dimensional (2D) electron-electron correlations among V atoms in the 1T phase and optimized in-planar electric transport. Our results highlight the phase engineering into electrode design for energy storage.

Palladium (Pd)-based sulfides have triggered extensive interest due to their unique properties and potential applications in the fields of electronics and optoelectronics. However, the synthesis of large-scale uniform PdS and PdS₂ nanofilms (NFs) remains an enormous challenge. In this work, 2-inch wafer-scale PdS and PdS₂ NFs with excellent stability can be controllably prepared via chemical vapor deposition combined with electron beam evaporation technique. The thickness of the pre-deposited Pd film and the sulfurization temperature are critical for the precise synthesis of PdS and PdS₂ NFs. A corresponding growth mechanism has been proposed based on our experimental results and Gibbs free energy calculations. The electrical transport properties of PdS and PdS₂ NFs were explored by conductive atomic force microscopy. Our findings have achieved the controllable growth of PdS and PdS₂ NFs, which may provide a pathway to facilitate PdS and PdS₂ based applications for next-generation high performance optoelectronic devices.

As typical quarternary copper-based chalcogenides, Cu-Zn-Sn-S nanocrystals (CZTS NCs) have emerged as a new-fashioned electrocatalyst in hydrogen evolution reactions (HERs). Oleylamine (OM), a reducing surfactant and solvent, plays a significant role in the assisting synthesis of CZTS nanocrystals due to the ligand effect. Herein, we adopted a facile one-pot colloidal method for achieving the structure evolution of CZTS NCs from 2D nanosheets to 1D nanorods assisted through the continuous addition of OM. During the process, the mechanism of OM-induced morphology evolution was further discussed. When merely adding pure 1-dodecanethiol (DDT) as the solvent, the CZTS nanosheets were obtained. As OM was gradually added to the reaction, the CZTS NCs began to grow along the sides of the nanosheets and gradually shrink at the top, followed by the formation of stable nanorods. In acidic electrolytic conditions, the CZTS NCs with 1.0 OM addition display the optimal HER activity with a low overpotential of 561 mV at 10 mA/cm² and a small Tafel slope of 157.6 mV/dec compared with other CZTS samples. The enhancement of HER activity could be attributed to the contribution of the synergistic effect of the diverse crystal facets to the reaction.

Modulation bandwidth enhancement in a directly modulated two-section distributed feedback (TS-DFB) laser based on a detuned loading effect is investigated and experimentally demonstrated. The results show that the 3-dB bandwidth of the TS-DFB laser is increased to 17.6 GHz and that chirp parameter can be reduced to 2.24. Compared to the absence of a detuned loading effect, there is a 4.6 GHz increase and a 2.45 reduction, respectively. After transmitting a 10 Gb/s non-return-to-zero (NRZ) signal through a 5-km fiber, the modulation eye diagram still achieves a large opening. Eight-channel laser arrays with precise wavelength spacing are fabricated. Each TS-DFB laser in the array has side mode suppression ratios (SMSR) > 49.093 dB and the maximum wavelength residual < 0.316 nm.

This manuscript explores the behavior of a junctionless tri-gate FinFET at the nano-scale region using SiGe material for the channel. For the analysis, three different channel structures are used: (a) tri-layer stack channel (TLSC) (Si-SiGe-Si), (b) double layer stack channel (DLSC) (SiGe-Si), (c) single layer channel (Si) (SLC). The I−V characteristics, subthreshold swing (SS), drain-induced barrier lowering (DIBL), threshold voltage (V_t), drain current (I_ON), OFF current (I_OFF), and ON-OFF current ratio (I_ON/I_OFF) are observed for the structures at a 20 nm gate length. It is seen that TLSC provides 21.3% and 14.3% more ON current than DLSC and SLC, respectively. The paper also explores the analog and RF factors such as input transconductance (g_m), output transconductance (g_ds), gain (g_m/g_ds), transconductance generation factor (TGF), cut-off frequency (f_T), maximum oscillation frequency (f_max), gain frequency product (GFP) and linearity performance parameters such as second and third-order harmonics (g_m2, g_m3), voltage intercept points (VIP₂, VIP₃) and 1-dB compression points for the three structures. The results show that the TLSC has a high analog performance due to more g_m and provides 16.3%, 48.4% more gain than SLC and DLSC, respectively and it also provides better linearity. All the results are obtained using the VisualTCAD tool.

Two-dimensional layered material/semiconductor heterostructures have emerged as a category of fascinating architectures for developing highly efficient and low-cost photodetection devices. Herein, we present the construction of a highly efficient flexible light detector operating in the visible-near infrared wavelength regime by integrating a PdTe₂ multilayer on a thin Si film. A representative device achieves a good photoresponse performance at zero bias including a sizeable current on/off ratio exceeding 10⁵, a decent responsivity of ~343 mAW⁻¹, a respectable specific detectivity of ~2.56 × 10¹² Jones, and a rapid response time of 4.5/379 μs, under 730 nm light irradiation. The detector also displays an outstanding long-term air stability and operational durability. In addition, thanks to the excellent flexibility, the device can retain its prominent photodetection performance at various bending radii of curvature and upon hundreds of bending tests. Furthermore, the large responsivity and rapid response speed endow the photodetector with the ability to accurately probe heart rate, suggesting a possible application in the area of flexible and wearable health monitoring.

The influence of the virtual guard ring width (GRW) on the performance of the p-well/deep n-well single-photon avalanche diode (SPAD) in a 180 nm standard CMOS process was investigated. TCAD simulation demonstrates that the electric field strength and current density in the guard ring are obviously enhanced when GRW is decreased to 1 μm. It is experimentally found that, compared with an SPAD with GRW=2 μm, the dark count rate (DCR) and afterpulsing probability (AP) of the SPAD with GRW=1 μm is significantly increased by 2.7 times and twofold, respectively, meanwhile, its photon detection probability (PDP) is saturated and hard to be promoted at over 2 V excess bias voltage. Although the fill factor (FF) can be enlarged by reducing GRW, the dark noise of devices is negatively affected due to the enhanced trap-assisted tunneling (TAT) effect in the 1 μm guard ring region. By comparison, the SPAD with GRW=2 μm can achieve a better trade-off between the FF and noise performance. Our study provides a design guideline for guard rings to realize a low-noise SPAD for large-array applications.

This letter showcases the successful fabrication of an enhancement-mode (E-mode) buried p-channel GaN field-effect-transistor on a standard p-GaN/AlGaN/GaN-on-Si power HEMT substrate. The transistor exhibits a threshold voltage (V_TH) of −3.8 V, a maximum ON-state current (I_ON) of 1.12 mA/mm, and an impressive I_ON/I_OFF ratio of 10⁷. To achieve these remarkable results, an H plasma treatment was strategically applied to the gated p-GaN region, where a relatively thick GaN layer (i.e., 70 nm) was kept intact without aggressive gate recess. Through this treatment, the top portion of the GaN layer was converted to be hole-free, leaving only the bottom portion p-type and spatially separated from the etched GaN surface and gate-oxide/GaN interface. This approach allows for E-mode operation while retaining high-quality p-channel characteristics.

This article reports on the development of a simple two-step lithography process for double barrier quantum well (DBQW) InGaAs/AlAs resonant tunneling diode (RTD) on a semi-insulating indium phosphide (InP) substrate using an air-bridge technology. This approach minimizes processing steps, and therefore the processing time as well as the required resources. It is particularly suited for material qualification of new epitaxial layer designs. A DC performance comparison between the proposed process and the conventional process shows approximately the same results. We expect that this novel technique will aid in the recent and continuing rapid advances in RTD technology.