This paper reports the successful fabrication of a GaN-on-Si high electron mobility transistor (HEMT) with a 1702 V breakdown voltage (BV) and low current collapse. The strain and threading dislocation density were well-controlled by 100 pairs of AlN/GaN superlattice buffer layers. Relative to the carbon-doped GaN spacer layer, we grew the AlGaN back barrier layer at a high temperature, resulting in a low carbon-doping concentration. The high-bandgap AlGaN provided an effective barrier for blocking leakage from the channel to substrate, leading to a BV comparable to the ordinary carbon-doped GaN HEMTs. In addition, the AlGaN back barrier showed a low dispersion of transiently pulsed I_D under substrate bias, implying that the buffer traps were effectively suppressed. Therefore, we obtained a low-dynamic on-resistance with this AlGaN back barrier. These two approaches of high BV with low current collapse improved the device performance, yielding a device that is reliable in power device applications.

Two-dimensional layered material Molybdenum disulfide (MoS₂) exhibits a flat surface without dangling bonds and is expected to be a suitable surface-enhanced Raman scattering (SERS) substrate for the detection of organic molecules. However, further fabrication of nanostructures for enhancement of SERS is necessary because of the low detection efficiency of MoS₂. In this paper, period-distribution Si/MoS₂ core/shell nanopillar (NP) arrays were fabricated for SERS. The MoS₂ thin films were formed on the surface of Si NPs by sulfurizing the MoO₃ thin films coated on the Si NP arrays. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were performed to characterize Si/MoS₂ core-shell nanostructure. In comparison with a bare Si substrate and MoS₂ thin film, the use of Si/MoS₂ core-shell NP arrays as SERS substrates enhances the intensity of each SERS signal peak for Rhodamine 6G (R6G) molecules, and especially exhibits about 75-fold and 7-fold enhancements in the 1361 cm⁻¹ peak signal, respectively. We suggest that the Si/MoS₂ core-shell NP arrays with larger area could absorb more R6G molecules and provide larger interfaces between MoS₂ and R6G molecules, leading to higher opportunity of charge transfer process and exciton transitions. Therefore, the Si/MoS₂ core/shell NP arrays could effectively enhance SERS signal and serve as excellent SERS substrates in biomedical detection.

In this article, we propose the novel core-shell Si/InxGa $_{{1}- {x}}$ As FinFETs, where an In $_{{0}.{53}}$ Ga $_{{0}.{47}}$ As shell channel was epitaxially grown on a silicon core fin. Based on the model calibrated using conventional bulk In $_{{0}.{53}}$ Ga $_{{0}.{47}}$ As FinFET, the device characteristics, including dc and RF performance of the core-shell FinFET, were analyzed and compared with the bulk FinFET. Due to the conduction band offset between InxGa $_{{1}- {x}}$ As shell and Si fin, a quantum well is formed in the InxGa $_{{1}- {x}}$ As channel region, which is lying between the high dielectric constant (HK) gate and the Si core. The advantages of the core-shell FinFET include increasing the gate controllability, enhancing the effective bandgap, and reducing the leakage current, while the on-state performance in transconductance ( ${g}_{m}\text {)}$ and drain current ( ${I}_{\text {ON}}\text {)}$ is maintained. The effects of varying the channel thickness, length, and the indium content of the InxGa $_{{1}- {x}}$ As shell are also explored in both dc and RF aspects. The results show that the core-shell FinFET exhibits superior characteristics in terms of leakage current, subthreshold swing, and drain-induced barrier lowering, owing to its superior gate controllability, with comparable RF performance in current gain cutoff frequency ( ${f}_{t} \gt 400$ GHz for 50-nm ${L}_{\text {Ch}}\text {)}$ with the bulk FinFET. The major objective of this article is to provide the possible directions for the design of the Si/InxGa $_{{1}- {x}}$ As core-shell FinFET for future device applications.

The fabrication of heterogeneous p-SiGe/n-Si channel CFETs presents significant challenges. In a single fin structure, selectively etching the Si layer while preserving the SiGe layer for the p-FET and selectively etching the SiGe layer while preserving the Si layer for the n-FET requires two opposite etching steps. This process becomes particularly complex because of the additional local lithography required. In this study, CFETs with multiply stacked p-SiGe/n-Si nanosheet channels by using Ge interlayers as sacrificial layers are demonstrated based on the wafer-bonding process flow.

This study utilized semiconductor processing techniques to fabricate patterned silicon (Si) substrates with arrays of inverted pyramid-shaped micro-pits by etching. Molybdenum trioxide (MoO₃) was then deposited on these patterned Si substrates using a thermal evaporation system, followed by two-stage sulfurization in a high-temperature furnace to grow MoS₂ thin films consisting of only a few atomic layers. During the dropwise titration of Rhodamine 6G (R6G) solution, a longitudinal electric field was applied using a Keithley 2400 (Cleveland, OH, USA) source meter. Raman mapping revealed that under a 100 mV condition, the analyte R6G molecules were effectively confined within the pits. Due to its two-dimensional structure, MoS₂ provides a high surface area and supports a surface-enhanced Raman scattering (SERS) charge transfer mechanism. The SERS results demonstrated that the intensity in the pits of the few-layer MoS₂/patterned Si SERS substrate was approximately 274 times greater compared to planar Si, with a limit of detection reaching 10⁻⁵ M. The experimental results confirm that this method effectively resolves the issue of random distribution of analyte molecules during droplet evaporation, thereby enhancing detection sensitivity and stability.